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NASA Astrophysics Data System (ADS)
This chapter reviews the data mining methods recently developed to solve standard data problems in weak gravitational lensing. We detail the different steps of the weak lensing data analysis along with the different techniques dedicated to these applications. An overview of the different techniques currently used will be given along with future prospects. Until about 30 years ago, astronomers thought that the Universe was composed almost entirely of ordinary matter: protons, neutrons, electrons, and atoms. The field of weak lensing has been motivated by the observations made in the last decades showing that visible matter represents only about 4-5% of the Universe (see Figure 14.1). Currently, the majority of the Universe is thought to be dark, that is, does not emit electromagnetic radiation. The Universe is thought to be mostly composed of an invisible, pressure less matter - potentially relic from higher energy theories - called "dark matter" (20-21%) and by an even more mysterious term, described in Einstein equations as a vacuum energy density, called "dark energy" (70%). This "dark" Universe is not well described or even understood; its presence is inferred indirectly from its gravitational effects, both on the motions of astronomical objects and on light propagation. So this point could be the next breakthrough in cosmology. Today's cosmology is based on a cosmological model that contains various parameters that need to be determined precisely, such as the matter density parameter Omega_m or the dark energy density parameter Omega_lambda. Weak gravitational lensing is believed to be the most promising tool to understand the nature of dark matter and to constrain the cosmological parameters used to describe the Universe because it provides a method to directly map the distribution of dark matter (see [1,6,60,63,70]). From this dark matter distribution, the nature of dark matter can be better understood and better constraints can be placed on dark energy, which affects the evolution of structures. Gravitational lensing is the process by which light from distant galaxies is bent by the gravity of intervening mass in the Universe as it travels toward us. This bending causes the images of background galaxies to appear slightly distorted, and can be used to extract important cosmological information. In the beginning of the twentieth century, A. Einstein predicted that massive bodies could be seen as gravitational lenses that bend the path of light rays by creating a local curvature in space time. One of the first confirmations of Einstein's new theory was the observation during the 1919 solar eclipse of the deflection of light from distant stars by the sun. Since then, a wide range of lensing phenomena have been detected. The gravitational deflection of light by mass concentrations along light paths produces magnification, multiplication, and distortion of images. These lensing effects are illustrated by Figure 14.2, which shows one of the strongest lenses observed: Abell 2218, a very massive and distant cluster of galaxies in the constellation Draco. The observed gravitational arcs are actually the magnified and strongly distorted images of galaxies that are about 10 times more distant than the cluster itself. These strong gravitational lensing effects are very impressive but they are very rare. Far more prevalent are weak gravitational lensing effects, which we consider in this chapter, and in which the induced distortion in galaxy images is much weaker. These gravitational lensing effects are now widely used, but the amplitude of the weak lensing signal is so weak that its detection relies on the accuracy of the techniques used to analyze the data. Future weak lensing surveys are already planned in order to cover a large fraction of the sky with high accuracy, such as Euclid [68]. However, improving accuracy also places greater demands on the methods used to extract the available information.
Pires, Sandrine; Starck, Jean-Luc; Leonard, Adrienne; R�fr�gier, Alexandre
The Bianchi identity and weak gravitational lensing
NASA Astrophysics Data System (ADS)
We consider the Bianchi identity as a field equation for the distortion of the shapes of images produced by weak gravitational lensing. Using the spin coefficient formalism of Newman and Penrose (1962 J. Math. Phys. 3 566 78), we show that certain complex components of the Weyl and Ricci curvature tensors are directly related to fundamental observables in weak gravitational lensing. In the case of weak gravitational fields, we then show that the Bianchi identity provides a field equation for the Ricci tensor assuming a known Weyl tensor. From the Bianchi identity, we derive the integral equation for weak lensing presented by Miralda-Escude (1996 IAU Symp. vol 173 p 131), thus making the Bianchi identity a first principles equation of weak gravitational lensing. This equation is integrated in the important case of an axially symmetric lens and explicitly demonstrated in the case of a point lens and a singular isothermal sphere (SIS) model.
Kling, Thomas P.; Keith, Brian
Weak gravitational lensing of intrinsically aligned galaxies
NASA Astrophysics Data System (ADS)
Subject of this paper is the weak lensing effect on galaxies that show intrinsically correlated ellipticities. In our model, we investigate the distortion of the ellipticity field if the galaxies experience an apparent shift in their position by weak lensing deflection and compare this effect to the shearing effect induced by tidal fields. Starting with a derivation of intrinsic ellipticity spectra by employing a tidal torquing model generating galactic angular momenta, we model the galaxy ellipticity by assuming that the galactic disc forms perpendicularly to the host halo angular momentum direction and derives intrinsic ellipticity E-mode and B-mode spectra from the angular momentum statistics. The lensing effect on the ellipticity field is modelled by employing the methodology developed in the framework of lensing of the cosmic microwave background polarization. For Euclid, ellipticity correlations are altered by lensing deflection on multipoles ? ? 1000 by �5 per cent for the ellipticity E modes and �30 per cent for the B modes, while a shallower survey would exhibit larger changes on larger angular scales. In addition to the convolving effect of lensing on the ellipticity spectra, we investigate the E/B-mode conversion and discuss the possibility of measuring correlations between different multipoles, which is evoked by the homogeneity breaking effect of the lensing displacement. Our conclusion is that although shape correlations generated by weak gravitational shear is dominant, the shifting effect due to lensing is shaping the ellipticity spectra on small angular scales and causing a number of interesting phenomena, which might be observable by future surveys.
Giahi-Saravani, Aram; Sch�fer, Bj�rn Malte
Atomic Inference from Weak Gravitational Lensing Data
We present a novel approach to reconstructing the projected mass distribution from the sparse and noisy weak gravitational lensing shear data. The reconstructions are regularized via the knowledge gained from numerical simulations of clusters, with trial mass distributions constructed from n NFW profile ellipsoidal components. The parameters of these ''atoms'' are distributed a priori as in the simulated clusters. Sampling the mass distributions from the atom parameter probability density function allows estimates of the properties of the mass distribution to be generated, with error bars. The appropriate number of atoms is inferred from the data itself via the Bayesian evidence, and is typically found to be small, reecting the quality of the data. Ensemble average mass maps are found to be robust to the details of the noise realization, and succeed in recovering the demonstration input mass distribution (from a realistic simulated cluster) over a wide range of scales. As an application of such a reliable mapping algorithm, we comment on the residuals of the reconstruction and the implications for predicting convergence and shear at specific points on the sky.
Marshall, Phil; /KIPAC, Menlo Park
Weak shear study of galaxy clusters by simulated gravitational lensing
NASA Astrophysics Data System (ADS)
Gravitational lensing has been simulated for numerical galaxy clusters in order to characterize the effects of substructure and shape variations of dark matter halos on the weak lensing properties of clusters. In order to analyze realistic galaxy clusters, 6 high-resolution Adaptive Refinement Tree N-body simulations of clusters with hydrodynamics are used, in addition to a simulation of one group undergoing a merger. For each cluster, the three-dimensional particle distribution is projected perpendicular to three orthogonal lines of sight, providing 21 projected mass density maps. The clusters have representative concentration and mass values for clusters in the concordance cosmology. Two gravitational lensing simulation methods are presented. In the first method, direct integration is used to calculate deflection angles. To overcome computational constraints inherent in this method, a distributed computing project was created for parallel computation. In addition to its use in gravitational lensing simulation, a description of the setup and function of this distributed computing project is presented as an alternative to in-house computing clusters, which has the added benefit of public enrollment in science and low cost. In the second method, shear maps are created using a fast Fourier transform method. From these shear maps, the effects of substructure and shape variation are related to observational gravitational lensing studies. Average shear in regions less than and greater than half of the virial radius demonstrates distinct dispersion, varying by 24% from the mean among the 21 maps. We estimate the numerical error in shear calculations to be of the order of 5%. Therefore, this shear dispersion is a reliable consequence of shape dispersion, correlating most strongly with the ratio of smallest-to-largest principal axis lengths of a cluster isodensity shell. On the other hand, image ellipticities, which are of great importance in mass reconstruction, are shown to have very little variance. However, tangential alignment of average image distortion is quite strong, making mass density peak locations easily resolvable.
Coss, David
The Intrinsic Alignment of Galaxies and Weak Gravitational Lensing
NASA Astrophysics Data System (ADS)
Galaxy intrinsic alignments (IA) are correlations between intrinsic galaxy shapes and the surrounding density field. These correlations can bias weak gravitational lensing measurements and are the most significant source of astrophysical uncertainty for the next generation of lensing experiments. Despite its importance, IA is poorly understood. The work presented here aims to improve our understanding through both modeling and measuring IA. First, we examine the most frequently employed IA model, the tidal (linear) alignment model, in which galaxy shapes are closely correlated with the surrounding gravitational tidal field. The tidal alignment model provides an accurate description of IA on large scales (r > 10 Mpc/h), as measured for luminous red galaxies in the Sloan Digital Sky Survey (SDSS). The IA amplitude for these objects, as determined in this analysis, will allow predictions for possible contamination in current and future lensing studies. We explore several ways in which the model could be improved and expanded, including how the relationship between galaxies and their host halos can modulate the strength of IA, as well as relevant effects on smaller scales (r < 10 Mpc/h). Second, we develop a method to separate IA from galaxy-galaxy lensing measurements using photometric redshift information. This technique allows the removal of contamination from the desired lensing signal while also providing a probe of IA in different galaxy populations. We employ this method to constrain fractional IA contamination in the SDSS lensing sample to 1-2%, finding that it is a subdominant source of uncertainty at the current level of statistical precision. These developments in both modeling and measurement techniques can be applied in future lensing analyses to mitigate potential contamination from IA. Such considerations will become more important as statistical precision continues to improve.
Blazek, Jonathan
Karhunen-Loeve Analysis for Weak Gravitational Lensing
NASA Astrophysics Data System (ADS)
In the past decade, weak gravitational lensing has become an important tool in the study of the universe at the largest scale, giving insights into the distribution of dark matter, the expansion of the universe, and the nature of dark energy. This thesis research explores several applications of Karhunen-Lo�ve (KL) analysis to speed and improve the comparison of weak lensing shear catalogs to theory in order to constrain cosmological parameters in current and future lensing surveys. This work addresses three related aspects of weak lensing analysis: Three-dimensional Tomographic Mapping: (Based on work published in Vanderplas et al 2011) We explore a new fast approach to three-dimensional mass mapping in weak lensing surveys. The KL approach uses a KL-based filtering of the shear signal to reconstruct mass structures on the line-of-sight, and provides a unified framework to evaluate the efficacy of linear reconstruction techniques. We find that the KL-based filtering leads to near-optimal angular resolution, and computation times which are faster than previous approaches. We also use the KL formalism to show that linear non-parametric reconstruction methods are fundamentally limited in their ability to resolve lens redshifts. Shear Peak Statistics with Incomplete Data: (Based on work published in Vanderplas et al 2012) We explore the use of KL eigenmodes for interpolation across masked regions in observed shear maps. Mass mapping is an inherently non-local calculation, meaning gaps in the data can have a significant effect on the properties of the derived mass map. Our KL mapping procedure leads to improvements in the recovery of detailed statistics of peaks in the mass map, which holds promise of improved cosmological constraints based on such studies. Two-point parameter estimation with KL modes: The power spectrum of the observed shear can yield powerful cosmological constraints. Incomplete survey sky coverage, however, can lead to mixing of power between Fourier modes, and obfuscate the cosmologically sensitive signal. We show that KL can be used to derive an alternate orthonormal basis for the problem which avoids mode-mixing and allows a convenient formalism for cosmological likelihood computations. Cosmological constraints derived using this method are shown to be competitive with those from the more conventional correlation function approach. We also discuss several aspects of the KL approach which will allow improved handling of correlated errors and redshift information in future surveys.
Vanderplas, Jacob T.
Weak gravitational lensing systematic errors in the dark energy survey
NASA Astrophysics Data System (ADS)
Dark energy is one of the most important unsolved problems in modern Physics, and weak gravitational lensing (WL) by mass structures along the line of sight ("cosmic shear") is a promising technique to learn more about its nature. However, WL is subject to numerous systematic errors which induce biases in measured cosmological parameters and prevent the development of its full potential. In this thesis, we advance the understanding of WL systematics in the context of the Dark Energy Survey (DES). We develop a testing suite to assess the performance of the shapelet-based DES WL measurement pipeline. We determine that the measurement bias of the parameters of our Point Spread Function (PSF) model scales as (S/N )-2, implying that a PSF S/N > 75 is needed to satisfy DES requirements. PSF anisotropy suppression also satisfies the requirements for source galaxies with S/N ? 45. For low-noise, marginally-resolved exponential galaxies, the shear calibration errors are up to about 0.06% (for shear values ? 0.075). Galaxies with S/N ? 75 present about 1% errors, sufficient for first-year DES data. However, more work is needed to satisfy full-area DES requirements, especially in the high-noise regime. We then implement tests to validate the high accuracy of the map between pixel coordinates and sky coordinates (astrometric solution), which is crucial to detect the required number of galaxies for WL in stacked images. We also study the effect of atmospheric dispersion on cosmic shear experiments such as DES and the Large Synoptic Survey Telescope (LSST) in the four griz bands. For DES (LSST), we find systematics in the g and r (g, r, and i) bands that are larger than required. We find that a simple linear correction in galaxy color is accurate enough to reduce dispersion shear systematics to insignificant levels in the r ( i) band for DES (LSST). More complex corrections will likely reduce the systematic cosmic-shear errors below statistical errors for LSST r band. However, g-band dispersion effects remain large enough for induced systematics to dominate the statistical error of both surveys, so cosmic-shear measurements should rely on the redder bands.
Plazas, Andres Alejandro
For several years astronomers have devoted considerable effort to finding and studying a class of celestial phenomena whose very existence depends on rare cosmic accidents. These are gravitational-lens events, which occur when two or more objects at different distances from the earth happen to lie along the same line of sight and so coincide in the sky. The radiation from the more distant object, typically a quasar, is bent by the gravitational field of the foreground object. The bending creates a cosmic mirage: distorted or multiple images of the background object. Such phenomena may reveal many otherwise undetectable features of the image source, of the foreground object and of the space lying between them. Such observations could help to resolve several fundamental questions in cosmology. In the past decade theoretical and observational research on gravitational lenses has grown rapidly and steadily. At this writing at least 17 candidate lens systems have been discussed in the literature. Of the 17 lens candidates reported so far in professional literature, only five are considered to have been reliably established by subsequent observations. Another three are generally regarded as weak or speculative cases with less than 50 percent chance of actually being lens systems. In the remaining nine cases the evidence is mixed or is sparse enough so that the final judgment could swing either way. As might be concluded, little of the scientific promise of gravitational lenses has yet been realized. The work has not yielded a clear value for the proportionality constant or any of the other fundamental cosmological parameter. 7 figs.
Turner, E.L.
Statistical properties of filaments in weak gravitational lensing
NASA Astrophysics Data System (ADS)
We study the weak lensing properties of filaments that connect clusters of galaxies through large cosmological N-body simulations. We select 4639 halo pairs with masses higher than 1014 h-1 M? from the simulations and investigate dark matter distributions between two haloes with ray-tracing simulations. In order to classify filament candidates, we estimate convergence profiles and perform profile fitting. We find that matter distributions between haloes can be classified in a plane of fitting parameters, which allows us to select straight filaments from the ray-tracing simulations. We also investigate the statistical properties of these filaments, finding them to be consistent with previous studies. We find that 35 per cent of halo pairs possess straight filaments, 4 per cent of which can be detected directly at signal-to-noise ratio S/N ? 2 with weak lensing. Furthermore, we study the statistical properties of haloes at the edges of filaments. We find that haloes are preferentially elongated along filamentary structures and are less massive with increasing filament mass. However, the dependence of these halo properties on the masses of straight filaments is very weak.
Higuchi, Yuichi; Oguri, Masamune; Shirasaki, Masato
Constraining Horava-Lifshitz gravity by weak and strong gravitational lensing
We discuss gravitational lensing in the Kehagias-Sfetsos space-time emerging in the framework of Horava-Lifshitz gravity. In weak lensing, we show that there are three regimes, depending on the value of {lambda}=1/{omega}d{sup 2}, where {omega} is the Horava-Lifshitz parameter and d characterizes the lensing geometry. When {lambda} is close to zero, light deflection typically produces two images, as in Schwarzschild lensing. For very large {lambda}, the space-time approaches flatness, therefore there is only one undeflected image. In the intermediate range of {lambda}, only the upper focused image is produced due to the existence of a maximal deflection angle {delta}{sub max}, a feature inexistent in the Schwarzschild weak lensing. We also discuss the location of Einstein rings, and determine the range of the Horava-Lifshitz parameter compatible with present-day lensing observations. Finally, we analyze in the strong lensing regime the first two relativistic Einstein rings and determine the constraints on the parameter range to be imposed by forthcoming experiments.
Horvath, Zsolt; Gergely, Laszlo A.; Keresztes, Zoltan; Harko, Tiberiu; Lobo, Francisco S. N. [Departments of Theoretical and Experimental Physics, University of Szeged, Dom ter 9, Szeged 6720 (Hungary); Department of Physics and Center for Theoretical and Computational Physics, University of Hong Kong, Pok Fu Lam Road (Hong Kong); Centro de Astronomia e Astrofisica da Universidade de Lisboa, Campo Grande, Edificio C8 1749-016 Lisboa (Portugal)
The Born and lens lens corrections to weak gravitational lensing angular power spectra
NASA Astrophysics Data System (ADS)
We revisit the estimation of higher order corrections to the angular power spectra of weak gravitational lensing. Extending a previous calculation of Cooray and Hu, we find two additional terms to the fourth order in potential perturbations of large-scale structure corresponding to corrections associated with the Born approximation and the neglect of line-of-sight coupling of two foreground lenses in the standard first order result. These terms alter the convergence (??), the lensing shear E-mode (epsiepsi), and their cross-correlation (?epsi) power spectra on large angular scales, but leave the power spectra of the lensing shear B-mode (??) and rotational (??) component unchanged as compared to previous estimates. The new terms complete the calculation of corrections to weak lensing angular power spectra associated with both the Born approximation and the lens lens coupling to an order in which the contributions are most significant. Taking these features together, we find that these corrections are unimportant for any weak lensing survey, including for a full sky survey limited by cosmic variance.
Shapiro, Charles; Cooray, Asantha
Measuring the galaxy-galaxy-mass three-point correlation function with weak gravitational lensing
We discuss the galaxy-galaxy-mass three-point correlation function and show how to measure it with weak gravitational lensing. The method entails choosing pairs of foreground lens galaxies, rotating them to the common coordinate system defined by the axis connecting them and then constructing a mean shear map by averaging the ellipticities of background source galaxies for a large number of foreground
David E. Johnston
Measuring the Galaxy-Galaxy-Mass Three-point Correlation Function with Weak Gravitational Lensing
We discuss the galaxy-galaxy-mass three-point correlation function and show\\u000ahow to measure it with weak gravitational lensing. The method entails choosing\\u000aa large of pairs of foreground lens galaxies and constructing a mean shear map\\u000awith respect to their axis, by averaging the ellipticities of background source\\u000agalaxies. An average mass map can be reconstructed from this shear map and
David E. Johnston
Rotation of the cosmic microwave background polarization from weak gravitational lensing.
When a cosmic microwave background (CMB) photon travels from the surface of last scatter through spacetime metric perturbations, the polarization vector may rotate about its direction of propagation. This gravitational rotation is distinct from, and occurs in addition to, the lensing deflection of the photon trajectory. This rotation can be sourced by linear vector or tensor metric perturbations and is fully coherent with the curl deflection field. Therefore, lensing corrections to the CMB polarization power spectra as well as the temperature-polarization cross correlations due to nonscalar perturbations are modified. The rotation does not affect lensing by linear scalar perturbations, but needs to be included when calculations go to higher orders. We present complete results for weak lensing of the full-sky CMB power spectra by general linear metric perturbations, taking into account both deflection of the photon trajectory and rotation of the polarization. For the case of lensing by gravitational waves, we show that the B modes induced by the rotation largely cancel those induced by the curl component of deflection. PMID:24580435
Dai, Liang
Self-Calibration Techniques for 3-point Intrinsic Alignment Correlations in Weak Gravitational Lensing Surveys
NASA Astrophysics Data System (ADS)
Weak gravitational lensing due to large scale structure (cosmic shear) has been shown to be contaminated by the intrinsic alignment (IA) of galaxies, which poses a barrier to precision weak lensing measurements in planned surveys. To address this contamination, we have extended the 2-point self-calibration techniques to the cosmic shear bispectrum, using information already measured in a weak lensing survey to self-calibrate the IA contamination. The 3-point self-calibration techniques use the redshift separation dependencies of the IA bispectra and the non-linear galaxy bias in order to isolate and remove the impact of the IA correlations on the cosmic shear signal. Using conservative estimates of photo-z accuracy, we find that planned surveys will be able to measure the IA redshift separation dependence over ranges in photo-z of 0.2 in the 3-point ellipticity auto-correlation. For the 3-point cross-correlations, we find that the self-calibration technique allows for reductions in the IA contamination by a factor of 10 or more over most scales and redshift bin choices and in all cases by a factor of 3-5 or more. The 3-point self-calibration techniques thus provide a means to greatly reduce the impact of IA contamination of the bispectrum in future measurements of cosmic shear.
Troxel, Michael A.; Ishak-Boushaki, M. B.
Improving three-dimensional mass mapping with weak gravitational lensing using galaxy clustering
NASA Astrophysics Data System (ADS)
Context. The weak gravitational lensing distortion of distant galaxy images (defined as sources) probes the projected large-scale matter distribution in the Universe. The availability of redshift information in galaxy surveys also allows us to recover the radial matter distribution to a certain degree. Aims: To improve quality in the mass mapping, we combine the lensing information with the spatial clustering of a population of galaxies (defined as tracers) that trace the matter density with a known galaxy bias. Methods: We construct a minimum-variance estimator for the 3D matter density that incorporates the angular distribution of galaxy tracers, which are coarsely binned in redshift. Merely the second-order bias of the tracers has to be known, which can in principle be self-consistently constrained in the data by lensing techniques. This synergy introduces a new noise component because of the stochasticity in the matter-tracer density relation. We give a description of the stochasticity noise in the Gaussian regime, and we investigate the estimator characteristics analytically. We apply the estimator to a mock survey based on the Millennium Simulation. Results: The estimator linearly mixes the individual lensing mass and tracer number density maps into a combined smoothed mass map. The weighting in the mix depends on the signal-to-noise ratio (S/N) of the individual maps and the correlation, R, between the matter and galaxy density. The weight of the tracers can be reduced by hand. For moderate mixing, the S/N in the mass map improves by a factor ~2-3 for R ? 0.4. Importantly, the systematic offset between a true and apparent mass peak distance (defined as z-shift bias) in a lensing-only map is eliminated, even for weak correlations of R ~ 0.4. Conclusions: If the second-order bias of tracer galaxies can be determined, the synergy technique potentially provides an option to improve redshift accuracy and completeness of the lensing 3D mass map. Herein, the aim is to visualise the spatial distribution of cluster-sized mass peaks. Our noise description of the estimator is accurate in the linear, Gaussian regime. However, its performance on sub-degree scales depends on the details in the galaxy bias mechanism and, hence, on the choice of the tracer population. Nonetheless, we expect that the mapping technique yields qualitatively reasonable results even for arcmin smoothing scales, as observed when this technique is applied to the mock survey with two different tracer populations.
Simon, Patrick
Weighing the Giants: Galaxy Cluster Cosmology Anchored by Weak Gravitational Lensing
NASA Astrophysics Data System (ADS)
The gas mass fractions and the distribution in mass and redshift of the galaxy cluster population provide powerful probes of cosmology, constraining the cosmic matter density (?m), the amplitude of the matter power spectrum (?8), properties of dark energy, and the mass of neutrinos, among other parameters. Historically, these tests have been limited by the absolute accuracy of cluster mass determinations. Here, mass measurements from weak lensing (made in the right way) have an advantage over estimates based on observations of the intracluster medium (ICM), because the former are nearly unbiased and can be straightforwardly tested against simulations. I will report new cosmological constraints obtained from an analysis of X-ray selected cluster samples, incorporating extensive gravitational lensing data from the Weighing the Giants project -- the first cluster cosmology study to consistently integrate a lensing mass calibration, including a rigorous quantification of all systematic uncertainties. Compared with earlier work, which had to incorporate larger systematic allowances associated with an ICM-based mass calibration, our joint constraints on ?m and ?8 are improved by a factor of 2. Including Cosmic Microwave Background and other cosmological probes in the analysis, we find no evidence for non-zero neutrino mass in the current data. This result is directly dependent on the absolute cluster mass calibration, and conflicts with some recent cluster results using ICM-based masses, highlighting the need for an accurate mass calibration (such as lensing provides). We also obtain tight constraints on dark energy models; for flat models with a constant equation of state (w), the cluster data alone yield w=?0.98�0.15. Our data, and their combination with other leading cosmological data sets, remain consistent with the concordance model of cosmology, with zero global curvature, dark energy as a non-evolving cosmological constant (w=?1), minimal neutrino mass, and gravity described by General Relativity.
Mantz, Adam; Von Der Linden, Anja; Allen, Steven W.; Applegate, Douglas; Kelly, Patrick; Morris, Glenn; Rapetti, David; Schmidt, Robert; Ebeling, Harald
Probing Dark Energy via Weak Gravitational Lensing with the Supernova Acceleration Probe (SNAP)
SNAP is a candidate for the Joint Dark Energy Mission (JDEM) that seeks to place constraints on the dark energy using two distinct methods. The first, Type Ia SN, is discussed in a separate white paper. The second method is weak gravitational lensing, which relies on the coherent distortions in the shapes of background galaxies by foreground mass structures. The excellent spatial resolution and photometric accuracy afforded by a 2-meter space-based observatory are crucial for achieving the high surface density of resolved galaxies, the tight control of systematic errors in the telescope's Point Spread Function (PSF), and the exquisite redshift accuracy and depth required by this project. These are achieved by the elimination of atmospheric distortion and much of the thermal and gravity loads on the telescope. The SN and WL methods for probing dark energy are highly complementary and the error contours from the two methods are largely orthogonal. The nominal SNAP weak lensing survey covers 1000 square degrees per year of operation in six optical and three near infrared filters (NIR) spanning the range 350 nm to 1.7 {micro}m. This survey will reach a depth of 26.6 AB magnitude in each of the nine filters and allow for approximately 100 resolved galaxies per square arcminute, {approx} 3 times that available from the best ground-based surveys. Photometric redshifts will be measured with statistical accuracy that enables scientific applications for even the faint, high redshift end of the sample. Ongoing work aims to meet the requirements on systematics in galaxy shape measurement, photometric redshift biases, and theoretical predictions.
Albert, J.; Aldering, G.; Allam, S.; Althouse, W.; Amanullah, R.; Annis, J.; Astier, P.; Aumeunier, M.; Bailey, S.; Baltay, C.; Barrelet, E.; Basa, S.; Bebek, C.; Bergstom, L.; Bernstein, G.; Bester, M.; Besuner, B.; Bigelow, B.; Blandford, R.; Bohlin, R.; Bonissent, A.; /Caltech /LBL, Berkeley /Fermilab /SLAC /Stockholm U. /Paris, IN2P3 /Marseille, CPPM /Marseille, Lab. Astrophys. /Yale U. /Pennsylvania U. /UC, Berkeley /Michigan U. /Baltimore, Space Telescope Sci. /Indiana U. /Caltech, JPL /Australian Natl. U., Canberra /American Astron. Society /Chicago U. /Cambridge U. /Saclay /Lyon, IPN
CFHTLenS: the relation between galaxy dark matter haloes and baryons from weak gravitational lensing
NASA Astrophysics Data System (ADS)
We present a study of the relation between dark matter halo mass and the baryonic content of their host galaxies, quantified through galaxy luminosity and stellar mass. Our investigation uses 154 deg2 of Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) lensing and photometric data, obtained from the CFHT Legacy Survey. To interpret the weak lensing signal around our galaxies, we employ a galaxy-galaxy lensing halo model which allows us to constrain the halo mass and the satellite fraction. Our analysis is limited to lenses at redshifts between 0.2 and 0.4, split into a red and a blue sample. We express the relationship between dark matter halo mass and baryonic observable as a power law with pivot points of 10^{11} h_{70}^{-2} L_{{?}} and 2� 10^{11} h_{70}^{-2} M_{{?}} for luminosity and stellar mass, respectively. For the luminosity-halo mass relation, we find a slope of 1.32 � 0.06 and a normalization of 1.19^{+0.06}_{-0.07}� 10^{13} h_{70}^{-1} M_{{?}} for red galaxies, while for blue galaxies the best-fitting slope is 1.09^{+0.20}_{-0.13} and the normalization is 0.18^{+0.04}_{-0.05}� 10^{13} h_{70}^{-1} M_{{?}}. Similarly, we find a best-fitting slope of 1.36^{+0.06}_{-0.07} and a normalization of 1.43^{+0.11}_{-0.08}� 10^{13} h_{70}^{-1} M_{{?}} for the stellar mass-halo mass relation of red galaxies, while for blue galaxies the corresponding values are 0.98^{+0.08}_{-0.07} and 0.84^{+0.20}_{-0.16}� 10^{13} h_{70}^{-1} M_{{? }}. All numbers convey the 68 per cent confidence limit. For red lenses, the fraction which are satellites inside a larger halo tends to decrease with luminosity and stellar mass, with the sample being nearly all satellites for a stellar mass of 2� 109 h_{70}^{-2} M_{{?}}. The satellite fractions are generally close to zero for blue lenses, irrespective of luminosity or stellar mass. This, together with the shallower relation between halo mass and baryonic tracer, is a direct confirmation from galaxy-galaxy lensing that blue galaxies reside in less clustered environments than red galaxies. We also find that the halo model, while matching the lensing signal around red lenses well, is prone to overpredicting the large-scale signal for faint and less massive blue lenses. This could be a further indication that these galaxies tend to be more isolated than assumed.
Velander, Malin; van Uitert, Edo; Hoekstra, Henk; Coupon, Jean; Erben, Thomas; Heymans, Catherine; Hildebrandt, Hendrik; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Bonnett, Christopher; Fu, Liping; Giodini, Stefania; Hudson, Michael J.; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta
Weak gravitational lensing due to large-scale structure of the universe
NASA Technical Reports Server (NTRS)
The effect of the large-scale structure of the universe on the propagation of light rays is studied. The development of the large-scale density fluctuations in the omega = 1 universe is calculated within the cold dark matter scenario using a smooth particle approximation. The propagation of about 10 to the 6th random light rays between the redshift z = 5 and the observer was followed. It is found that the effect of shear is negligible, and the amplification of single images is dominated by the matter in the beam. The spread of amplifications is very small. Therefore, the filled-beam approximation is very good for studies of strong lensing by galaxies or clusters of galaxies. In the simulation, the column density was averaged over a comoving area of approximately (1/h Mpc)-squared. No case of a strong gravitational lensing was found, i.e., no 'over-focused' image that would suggest that a few images might be present. Therefore, the large-scale structure of the universe as it is presently known does not produce multiple images with gravitational lensing on a scale larger than clusters of galaxies.
Jaroszynski, Michal; Park, Changbom; Paczynski, Bohdan; Gott, J. Richard, III
Mass and concentration estimates from weak and strong gravitational lensing: a systematic study
NASA Astrophysics Data System (ADS)
We study how well halo properties of galaxy clusters, such as mass and concentration, are recovered using lensing data. In order to generate a large sample of systems at different redshifts, we use the code MOKA. We measure halo mass and concentration using weak lensing data alone (WL), fitting to a Navarro, Frenk & White (NFW) profile the reduced tangential shear profile, or by combining weak and strong lensing data, by adding information about the size of the Einstein radius (WL+SL). For different redshifts, we measure the mass and the concentration biases and find that these are mainly caused by the random orientation of the halo ellipsoid with respect to the line of sight. Since our simulations account for the presence of a bright central galaxy, we perform mass and concentration measurements using a generalized NFW profile which allows for a free inner slope. This reduces both the mass and the concentration biases. We discuss how the mass function and the concentration-mass relation change when using WL and WL+SL estimates. We investigate how selection effects impact the measured concentration-mass relation showing that strong lens clusters may have a concentration 20-30 per cent higher than the average, at fixed mass, considering also the particular case of strong lensing selected samples of relaxed clusters. Finally, we notice that selecting a sample of relaxed galaxy clusters, as is done in some cluster surveys, explains the concentration-mass relation biases.
Giocoli, Carlo; Meneghetti, Massimo; Metcalf, R. Benton; Ettori, Stefano; Moscardini, Lauro
What is Gravitational Lensing?
July 28, 2009 Berkeley Lab summer lecture: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
Alexie Leauthaud and Reiko Nakajima
What is Gravitational Lensing?
July 28, 2009 Berkeley Lab summer lecture: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
Alexie Leauthaud and Reiko Nakajima
Probing high-redshift clusters with HST/ACS gravitational weak-lensing and Chandra x-ray observations
NASA Astrophysics Data System (ADS)
Clusters of galaxies, the largest gravitationally bound objects in the Universe, are useful tracers of cosmic evolution, and particularly detailed studies of still-forming clusters at high-redshifts can considerably enhance our understanding of the structure formation. We use two powerful methods that have become recently available for the study of these distant clusters: spaced- based gravitational weak-lensing and high-resolution X-ray observations. Detailed analyses of five high-redshift (0.8 < z < 1.3) clusters are presented based on the deep Advanced Camera for Surveys (ACS) and Chandra X-ray images. We show that, when the instrumental characteristics are properly understood, the newly installed ACS on the Hubble Space Telescope (HST) can detect subtle shape distortions of background galaxies down to the limiting magnitudes of the observations, which enables the mapping of the cluster dark matter in unprecedented high-resolution. The cluster masses derived from this HST /ACS weak-lensing study have been compared with those from the re-analyses of the archival Chandra X-ray data. We find that there are interesting offsets between the cluster galaxy, intracluster medium (ICM), and dark matter centroids, and possible scenarios are discussed. If the offset is confirmed to be uniquitous in other clusters, the explanation may necessitate major refinements in our current understanding of the nature of dark matter, as well as the cluster galaxy dynamics. CL0848+4452, the highest-redshift ( z = 1.27) cluster yet detected in weak-lensing, has a significant discrepancy between the weak- lensing and X-ray masses. If this trend is found to be severe and common also for other X-ray weak clusters at redshifts beyond the unity, the conventional X-ray determination of cluster mass functions, often inferred from their immediate X-ray properties such as the X-ray luminosity and temperature via the so-called mass-luminosity (M-L) and mass-temperature (M-T) relations, will become highly unstable in this redshift regime. Therefore, the relatively unbiased weak-lensing measurements of the cluster mass properties can be used to adequately calibrate the scaling relations in future high-redshift cluster investigations.
Jee, Myungkook James
Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component {Omega}{sub X} at greater than 99% confidence for an equation-of-state parameter -2.5 {<=} w {<=} -0.1. For the case w = -1, we find a value for the cosmological constant density parameter {Omega}{sub {Lambda}} = 0.85{sup +0.044}{sub -}0{sub .19} (68% CL) and detect cosmic acceleration (q{sub 0} < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys.
Taylor, James E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, Ontario N2L 3G1 (Canada); Massey, Richard J. [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8583 (Japan); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Rhodes, Jason; Ellis, Richard; Scoville, Nick [California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kitching, Thomas D. [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Capak, Peter [Spitzer Science Center, 314-6 Caltech, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany); Ilbert, Olivier; Kneib, Jean-Paul [LAM, CNRS-UNiv Aix-Marseille, 38 rue F. Joliot-Curis, 13013 Marseille (France); Jullo, Eric [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Koekemoer, Anton M., E-mail: firstname.lastname@example.com [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
Weak lensing and cosmological investigation
NASA Astrophysics Data System (ADS)
In the last few years the scientific community has been dealing with the challenging issue of identifying the dark energy component. We regard weak gravitational lensing as a brand new, and extremely important, tool for cosmological investigation in this field. In fact, the features imprinted on the Cosmic Microwave Background radiation by the lensing from the intervening distribution of matter represent a pretty unbiased estimator, and can thus be used for putting constraints on different dark energy models. This is true in particular for the magnetic-type B-modes of CMB polarization, whose unlensed spectrum at large multipoles (l ~= 1000) is very small even in presence of an amount of gravitational waves as large as currently allowed by the experiments: therefore, on these scales the lensing phenomenon is the only responsible for the observed power, and this signal turns out to be a faithful tracer of the dark energy dynamics. We first recall the formal apparatus of the weak lensing in extended theories of gravity, introducing the physical observables suitable to cast the bridge between lensing and cosmology, and then evaluate the amplitude of the expected effect in the particular case of a Non-Minimally-Coupled model, featuring a quadratic coupling between quintessence and Ricci scalar.
Acquaviva, Viviana
Gravitational lensing by 3-d matter distributions
NASA Astrophysics Data System (ADS)
Gravitational lensing studies have become an important tool for studying galactic structure and cluster morphology because the methods do not rely heavily on specific knowledge of cosmological parameters. To date, lensing studies use a weak- field, thin lens approximation where the lensing action is assumed to occur in a two-dimensional lens plane. We compare this approximation with the results of integrating the null geodesic equations for weak field metrics with ``standard'' three dimensional mass distributions.
Kling, Thomas
NSDL National Science Digital Library
The Gravitational Lensing model simulates the result of the deflection of photons as they pass through the warped space-time of a gravitational field of stars, clusters of galaxies or dark matter. In the simulation you can examine the effect caused by a gravitational lens in three different cases: 1. A point-mass lens and a point mass source. 2. A point-mass lens and an extended source. 3. A softened isothermal sphere lens and an extended source. You can modify this simulation if you have Ejs installed by right-clicking within the plot and selecting "Open Ejs Model" from the pop-up menu item. The Gravitational Lensing model was created using the Easy Java Simulations (Ejs) modeling tool. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the ejs_ehu_general_relativity_Gravitational_Lensing.jar file will run the program if Java is installed. Please note that this resource requires at least version 1.5 of Java (JRE).
Sancho, Ms. M.
Measuring the Geometry of the Universe from Weak Gravitational Lensing behind Galaxy Groups in the HST COSMOS Survey
NASA Astrophysics Data System (ADS)
Gravitational lensing can provide pure geometric tests of the structure of spacetime, for instance by determining empirically the angular diameter distance-redshift relation. This geometric test has been demonstrated several times using massive clusters which produce a large lensing signal. In this case, matter at a single redshift dominates the lensing signal, so the analysis is straightforward. It is less clear how weaker signals from multiple sources at different redshifts can be stacked to demonstrate the geometric dependence. We introduce a simple measure of relative shear which for flat cosmologies separates the effect of lens and source positions into multiplicative terms, allowing signals from many different source-lens pairs to be combined. Applying this technique to a sample of groups and low-mass clusters in the COSMOS survey, we detect a clear variation of shear with distance behind the lens. This represents the first detection of the geometric effect using weak lensing by multiple, low-mass groups. The variation of distance with redshift is measured with sufficient precision to constrain the equation of state of the universe under the assumption of flatness, equivalent to a detection of a dark energy component ? X at greater than 99% confidence for an equation-of-state parameter -2.5 <= w <= -0.1. For the case w = -1, we find a value for the cosmological constant density parameter ?? = 0.85+0.044 -0.19 (68% CL) and detect cosmic acceleration (q 0 < 0) at the 98% CL. We consider the systematic uncertainties associated with this technique and discuss the prospects for applying it in forthcoming weak-lensing surveys. Based on observations with the NASA/ESA Hubble Space Telescope obtained at the Space Telescope Science Institute, which is operated by AURA Inc. under the NASA contract NAS 5-26555; the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the European Southern Observatory under the Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation.
Taylor, James E.; Massey, Richard J.; Leauthaud, Alexie; George, Matthew R.; Rhodes, Jason; Kitching, Thomas D.; Capak, Peter; Ellis, Richard; Finoguenov, Alexis; Ilbert, Olivier; Jullo, Eric; Kneib, Jean-Paul; Koekemoer, Anton M.; Scoville, Nick; Tanaka, Masayuki
DES Gravitational Lensing Results
NASA Astrophysics Data System (ADS)
I will give an overview of the current state of the weak-lensing data analysis, focussing on systematics tests to validate the quality of the survey images, and highlight the first results obtained from observations during the Science Verification period.
Melchior, Peter
We study the power of upcoming weak lensing surveys to probe dark energy. Dark energy modifies the distance-redshift relation as well as the matter power spectrum, both of which affect the weak lensing convergence power spectrum. Some dark-energy models predict additional clustering on very large scales, but this probably cannot be detected by weak lensing alone due to cosmic variance.
Dragan Huterer
Issues in Exact Gravitational Lensing
NASA Astrophysics Data System (ADS)
The gravitational lensing problem is discussed in an exact setting - namely, without the use of approximations such as weak fields or thin lenses. In particular, the distortion of the images of elliptical sources is described in terms of three parameters (the semiaxes ratio, the area and orientation of the ellipse), and evolution equations for these parameters are derived. The evolution equations determine the image's shape from the source's shape, which acts as inital data, or viceversa. The evolution equations are first-order, nonlinear coupled ordinary differential equations for the three parameters, in which the divergence and shear of the past lightcone of the observer act as known sources. The deflector is encoded in the divergence and shear of the past lightcone of the observer by means of the optical equations.
Frittelli, Simonetta; Kling, Thomas P.; Newman, Ezra T.
Test of Gravity on Large Scales with Weak Gravitational Lensing and Clustering Measurements of SDSS Luminous Red Galaxies
NASA Astrophysics Data System (ADS)
We perform a test of gravity on large scales (5-50 Mpc/h) using 70,000 luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) DR7 with redshifts 0.16 Reyes, Reinabelle; Mandelbaum, R.; Seljak, U.; Gunn, J.; Lombriser, L. 2009-01-01
Reyes, Reinabelle; Mandelbaum, R.; Seljak, U.; Gunn, J.; Lombriser, L.
Nbody Simulations and Weak Gravitational Lensing using new HPC-Grid resources: the PI2S2 project
NASA Astrophysics Data System (ADS)
We present the main project of the new grid infrastructure and the researches, that have been already started in Sicily and will be completed by next year. The PI2S2 project of the COMETA consortium is funded by the Italian Ministry of University and Research and will be completed in 2009. Funds are from the European Union Structural Funds for Objective 1 regions. The project, together with a similar project called Trinacria GRID Virtual Laboratory (Trigrid VL), aims to create in Sicily a computational grid for e-science and e-commerce applications with the main goal of increasing the technological innovation of local enterprises and their competition on the global market. PI2S2 project aims to build and develop an e-Infrastructure in Sicily, based on the grid paradigm, mainly for research activity using the grid environment and High Performance Computer systems. As an example we present the first results of a new grid version of FLY a tree Nbody code developed by INAF Astrophysical Observatory of Catania, already published in the CPC program Library, that will be used in the Weak Gravitational Lensing field.
Becciani, U.; Antonuccio-Delogu, V.; Costa, A.; Comparato, M.
Dark Haloes as Seen with Gravitational Lensing
NASA Astrophysics Data System (ADS)
Dark matter is an important ingredient of galaxies, as was recognized early on by Ken Freeman himself! Evidence for dark matter halos is still indirect, based on analysing motions of tracers such as gas and stars. In a sense the visible galaxy is the mask through which we can study the dark matter. Light rays are also sensitive to gravitational fields and dark haloes cause observable gravitational lensing effects. There are three regimes: microlensing (which probes the clumpiness of dark matter haloes), strong lensing (sensitive to the inner mass distribution) and weak lensing (which can probe haloes out to 100 s of kpc from the centre). This review will concentrate on weak lensing and describe a new survey, the Kilo-Degree Survey (KiDS), that is designed to study galaxy halo masses, extents, and shapes as a function of environment, galaxy type, and redshift.
Kuijken, Konrad
Weak lensing of the primary CMB bispectrum
The bispectrum of cosmic microwave background (CMB) anisotropies is a well-known probe of the non-Gaussianity of primordial perturbations. Just as the intervening large-scale structure modifies the CMB angular power spectrum through weak gravitational lensing, the CMB primary bispectrum generated at the last scattering surface is also modified by lensing. We discuss the lensing modification to the CMB bispectrum and show that lensing leads to an overall decrease in the amplitude of the primary bispectrum at multipoles of interest between 100 and 2000 through additional smoothing introduced by lensing. Since weak lensing is not accounted for in current estimators of the primordial non-Gaussianity parameter, the existing measurements of f{sub NL} of the local model with WMAP out to l{sub max}{approx}750 is biased low by about 6%. For a high resolution experiment such as Planck, the lensing modification to the bispectrum must be properly included when attempting to estimate the primordial non-Gaussianity or the bias will be at the level of 30%. For Planck, weak lensing increases the minimum detectable value for the non-Gaussianity parameter of the local type f{sub NL} to 7 from the previous estimate of about 5 without lensing. The minimum detectable value of f{sub NL} for a cosmic variance limited experiment is also increased from less than 3 to {approx}5.
Cooray, Asantha; Sarkar, Devdeep; Serra, Paolo [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)
Strong Gravitational Lensing with LSST
LSST will find more strong gravitational lensing events than any other survey preceding it, and will monitor them all at a cadence of a few days to a few weeks. We can expect the biggest advances in strong lensing science made with LSST to be in those areas that benefit most from the large volume, and the high accuracy multi-filter
Philip J. Marshall; M. Bradac; G. Chartas; G. Dobler; A. Eliasdottir; E. Falco; C. D. Fassnacht; M. J. Jee; C. R. Keeton; M. Oguri; J. A. Tyson
Cosmological applications of gravitational lensing
NASA Astrophysics Data System (ADS)
In this thesis we use the gravitational lensing effect as a tool to tackle two rather different cosmological topics: the nature of the dark matter in galaxy halos, and the rotation of the universe. Firstly, we study the microlensing effect in the gravitational lens systems Q0957+561 and Q2237+0305. In these systems the light from the quasar shines directly through the lensing galaxy. Due to the relative motion of the quasar, the lensing galaxy, and the observer compact objects in the galaxy or galaxy halo cause brightness fluctuations of the light from the background quasar. We compare light curve data from a monitoring program of the double quasar Q0957+561 at the 3.5m telescope at Apache Point Observatory from 1995 to 1998 (Colley, Kundic & Turner 2000) with numerical simulations to test whether the halo of the lensing galaxy consists of massive compact objects (MACHOs). This test was first proposed by Gott (1981). We can exclude MACHO masses from 10^-6 M_sun up to 10^-2 M_sun for quasar sizes of less than 3x10^14 h_60^-0.5 cm if the MACHOs make up at least 50% of the dark halo. Secondly, we present new light curve data for the gravitationally lensed quadruple quasar Q2237+0305 taken at the 3.5m telescope at Apache Point Observatory from June 1995 to January 1998. Although the images were taken under variable, often poor seeing conditions and with coarse pixel sampling, photometry is possible for the two brighter quasar images A and B with the help from HST observations. We find independent evidence for a brightness peak in image A of 0.4 to 0.5 mag with a duration of at least 100 days, which indicates that microlensing has taken place in the lensing galaxy. Finally, we use the weak gravitational lensing effect to put limits on a class of Goedel-type rotating cosmologies described by Korotky & Obukhov (1996). In weak lensing studies the shapes of thousands of background galaxies are measured and averaged to reveal coherent gravitational distortions of the galaxy shapes by foreground matter distributions, or by the large-scale structure of space-time itself. We calculate the predicted shear as a function of redshift in Goedel-type rotating cosmologies and compare this to the upper limit on cosmic shear gamma_limit of approximately 0.04 from weak lensing studies. We find that Goedel-type models cannot have larger rotations omega than H_0=6.1x10^-11 h_60/year if this shear limit is valid for the whole sky. In dieser Arbeit benutze ich den Gravitationslinseneffekt als ein Werkzeug, um zwei recht unterschiedliche kosmologische Fragestellungen zu bearbeiten: die Natur der dunklen Materie in Galaxienhalos und die Rotation des Universums. Zuerst untersuche ich den Mikrolinseneffekt in den Gravitationlinsensystemen Q0957+561 und Q2237+0305. In diesen Systemen scheint das Licht eines Quasars durch die Linsengalaxie hindurch. Aufgrund der Relativbewegung zwischen Quasar, Linsengalaxie und Beobachter verursachen kompakte Objekte innerhalb der Galaxie oder dem Galaxienhalo Helligkeitsfluktuationen des Hintergrundquasars. Ich vergleiche die am 3.5m Teleskop des Apache Point Observatory zwischen 1995 und 1998 gewonnene Lichtkurve des Doppelquasars Q0957+561 (Colley, Kundic & Turner 2000) mit numerischen Simulationen, um zu untersuchen, ob der Halo der Linsengalaxie aus massiven kompakten Objekten (MACHOs) besteht. Dieser Test wurde zuerst von Gott (1981) vorgeschlagen. Ich kann MACHO-Massen von 10^-6 M_sun bis zu 10^-2 M_sun ausschliessen, sofern der Quasar kleiner ist als 3x10^14 h_60^-0.5 cm und MACHOs mehr als 50% des dunklen Halos ausmachen. Im zweiten Teil der Arbeit stelle ich neue Beobachtungsdaten fuer den Vierfachquasar Q2237+0305 vor, die am 3.5m Teleskop des Apache Point Observatory zwischen Juni 1995 und Januar 1998 gewonnen wurden. Obwohl die Daten bei veraenderlichen, oft schlechten Seeing Bedingungen und grober Pixelaufloesung aufgenommen wurden, ist die Photometrie der beiden helleren Quasarbilder A und B mit Hilfe von HST-Beobachtungen moeglich. Ich finde ein Helligkeitsmaximum in Bild A mit einer Amplitu
Schmidt, Robert W.
EDITORIAL: Focus on Gravitational Lensing
NASA Astrophysics Data System (ADS)
Gravitational lensing emerged as an observational field following the 1979 discovery of a doubly imaged quasar lensed by a foreground galaxy. In the 1980s and '90s dozens of other multiply imaged systems were observed, as well as time delay measurements, weak and strong lensing by galaxies and galaxy clusters, and the discovery of microlensing in our galaxy. The rapid pace of advances has continued into the new century. Lensing is currently one of best techniques for finding and mapping dark matter over a wide range of scales, and also addresses broader cosmological questions such as understanding the nature of dark energy. This focus issue of New Journal of Physics presents a snapshot of current research in some of the exciting areas of lensing. It provides an occasion to look back at the advances of the last decade and ahead to the potential of the coming years. Just about a decade ago, microlensing was discovered through the magnification of stars in our galaxy by invisible objects with masses between that of Jupiter and a tenth the mass of the Sun. Thus a new component of the mass of our galaxy, dubbed MACHOs, was established (though a diffuse, cold dark matter-like component is still needed to make up most of the galaxy mass). More recently, microlensing led to another exciting discovery�of extra-solar planets with masses ranging from about five times that of Earth to that of Neptune. We can expect many more planets to be discovered through ongoing surveys. Microlensing is the best technique for finding Earth mass planets, though it is not as productive overall as other methods and does not allow for follow up observations. Beyond planet hunting, microlensing has enabled us to observe previously inaccessible systems, ranging from the surfaces of other stars to the accretion disks around the black holes powering distant quasars. Galaxies and galaxy clusters at cosmological distances can produce dramatic lensing effects: multiple images of background galaxies or quasars which are strongly magnified and sheared. In the last decade, double and quadruply imaged systems due to galactic lenses have been studied with optical and radio observations. An interesting result obtained from the flux ratio 'anomalies' of quadruply imaged systems is the statistical detection of dark sub-clumps in galaxy halos. More broadly, while we have learned a lot about the mass distribution in lens galaxies and improved time delay constraints on the Hubble constant, the limitations of cosmological studies with strong lensing due to uncertainties in lens mass models have also come to be appreciated. That said, progress will no doubt continue with qualitative advances in observations such as astrometric counterparts to the flux anomalies, clever ideas such as the use of spectroscopic signatures to assemble the SLACS lens sample, and combining optical imaging, spectroscopy and radio data to continue the quest for a set of golden lenses to measure the Hubble constant. Galaxy clusters are a fascinating arena for studying the distribution of dark and baryonic matter. Weak and strong lensing information can be combined with dynamical information from the spectroscopic measurements of member galaxies and x-ray/Sunyaev Zeldovich measurements of the hot ionized gas. Hubble Space Telescope observations have yielded spectacular images of clusters, such as Abell 1689, which has over a hundred multiply imaged arcs. Mass measurements have progressed to the level of 10 percent accuracy for several clusters. Unfortunately, it is unclear if one can do much better for individual clusters given inherent limitations such as unknown projection effects. The statistical study of clusters is likely to remain a promising way to study dark matter, gravity theories, and cosmology. Techniques to combine weak and strong lensing information to obtain the mass distribution of clusters have also advanced, and work continues on parameter-free techniques that are agnostic to the relation of cluster light and mass. An interesting twist in cluster lensing was provided by the pos
Jain, Bhuvnesh
Environments of strong gravitational lenses
NASA Astrophysics Data System (ADS)
This dissertation focuses on determining the properties of the environments and the line-of-sight mass distributions for a sample of strong gravitational lenses as well as establishing their effects on the observed lens properties and the Hubble constant. Strong gravitational lenses ought to be able to provide important constraints for cosmology, however the lack of understanding of their large-scale environments has hindered their use. Here, we present a spectroscopic survey of the environments and lines of sight of 28 strong galaxy-mass lenses. We determine redshifts for 9698 galaxies in the fields of these lenses and identify 163 structures with at least five members in 26 fields. We find that 12 of 26 lenses are group members. Six of these groups are newly discovered. Overall, between 38-67% of lenses are in groups, and in 8-31% of the lenses the group makes a significant contribution to the lens potential. Line-of-sight structures are present in virtually every lens field, and in 19% of lenses the structures appear to be a significant perturbation to the lens potential. We consider the effect of the environment on H 0 derived from gravitational lenses. We find that, when the environment is ignored, lenses in groups predict a systematically higher value of H 0 , inconsistent at the 1? level with H 0 derived from isolated lenses. Correcting for the environment and line of sight structures brings the two values into agreement and lowers the combined value ( [Special characters omitted.] Without correction for the environment, the H0 values from strong lenses should be considered a strict upper limit. We explore the correlation between the observed lens properties and external perturbations from the observational perspective. We find that four-image lenses are statistically more likely to be in groups than two-image lenses. Furthermore, the distributions of convergences are statistically different for quads and doubles. This finding strongly supports the idea that the high quad-to-double ratios are at least partially due to the effect of the environment. We also examine the connections between flux anomalies and environment and the correlations between image separations and convergence. We find no significant links due to the limitations of our sample.
Momcheva, Ivelina Gospodinova
We introduce a new method for constraining the redshift distribution of a set of galaxies, using weak gravitational lensing shear. Instead of using observed shears and redshifts to constrain cosmological parameters, we ask how well the shears around clusters can constrain the redshifts, assuming fixed cosmological parameters. This provides a check on photometric redshifts, independent of source spectral energy distribution properties and therefore free of confounding factors such as misidentification of spectral breaks. We find that {approx}40 massive ({sigma}{sub v} = 1200 km s{sup -1}) cluster lenses are sufficient to determine the fraction of sources in each of six coarse redshift bins to {approx}11%, given weak (20%) priors on the masses of the highest-redshift lenses, tight (5%) priors on the masses of the lowest-redshift lenses, and only modest (20%-50%) priors on calibration and evolution effects. Additional massive lenses drive down uncertainties as N{sub lens}{sup -1/2}, but the improvement slows as one is forced to use lenses further down the mass function. Future large surveys contain enough clusters to reach 1% precision in the bin fractions if the tight lens-mass priors can be maintained for large samples of lenses. In practice this will be difficult to achieve, but the method may be valuable as a complement to other more precise methods because it is based on different physics and therefore has different systematic errors.
Wittman, D.; Dawson, W. A., E-mail: email@example.com [Physics Department, University of California, Davis, CA 95616 (United States)
Gravitational Lenses in the Classroom
ERIC Educational Resources Information Center
It is not common to introduce current astronomy in school lessons. This article presents a set of experiments about gravitational lenses. It is normal to simulate them by means of computers, but it is very simple to simulate similar effects using a drinking glass full of liquid or using only the glass base. These are, of course, cheap and easy�
Ros, Rosa M.
NASA Technical Reports Server (NTRS)
The NASA Hubble Space Telescope serendipitous survey of the sky has uncovered exotic patterns, rings, arcs and crosses that are all optical mirages produced by a gravitational lens, nature's equivalent of having giant magnifying glass in space. Shown are the top 10 lens candidates uncovered in the deepest 100 Hubble fields. Hubble's sensitivity and high resolution allow it to see faint and distant lenses that cannot be detected with ground-based telescopes whose images are blurred by Earth's atmosphere. [Top Left] - HST 01248+0351 is a lensed pair on either side of the edge-on disk lensing galaxy. [Top Center] - HST 01247+0352 is another pair of bluer lensed source images around the red spherical elliptical lensing galaxy. Two much fainter images can be seen near the detection limit which might make this a quadruple system. [Top Right] - HST 15433+5352 is a very good lens candidate with a bluer lensed source in the form of an extended arc about the redder elliptical lensing galaxy. [Middle Far Left] - HST 16302+8230 could be an 'Einstein ring' and the most intriguing lens candidate. It has been nicknamed the 'the London Underground' since it resembles that logo. [Middle Near Left] - HST 14176+5226 is the first, and brightest lens system discovered in 1995 with the Hubble telescope. This lens candidate has now been confirmed spectroscopically using large ground-based telescopes. The elliptical lensing galaxy is located 7 billion light-years away, and the lensed quasar is about 11 billion light-years distant. [Middle Near Right] - HST 12531-2914 is the second quadruple lens candidate discovered with Hubble. It is similar to the first, but appears smaller and fainter. [Middle Far Right] - HST 14164+5215 is a pair of bluish lensed images symmetrically placed around a brighter, redder galaxy. [Bottom Left] - HST 16309+8230 is an edge-on disk-like galaxy (blue arc) which has been significantly distorted by the redder lensing elliptical galaxy. [Bottom Center] - HST 12368+6212 is a blue arc in the Hubble Deep Field (HDF). [Bottom Right] - HST 18078+4600 is a blue arc caused by the gravitational potential of a small group of 4 galaxies. Credit: Kavan Ratnatunga (Carnegie Mellon Univ.) and NASA
Weak gravitational lensing has proven to be a powerful tool to map directly the distribution of dark matter in the universe. The technique, currently used, relies on the accurate measurement of the gravitational shear that corresponds to the first-order distortion of the background galaxy images. More recently, a new technique has been introduced that relies on the accurate measurement of the gravitational flexion that corresponds to the second-order distortion of the background galaxy images. This technique should probe structures on smaller scales than that of shear analysis. The goal of this paper is to compare the ability of shear and flexion to reconstruct the dark matter distribution by taking into account the dispersion in shear and flexion measurements. Our results show that the flexion is less sensitive than shear for constructing the convergence maps on scales that are physically feasible for mapping, meaning that flexion alone should not be used to do convergence map reconstruction, even on small scales.
Pires, S. [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU/SEDI-SAP, Service d'Astrophysique, CEA Saclay, Orme des Merisiers, 91191 Gif-sur-Yvette (France); Amara, A. [Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland)
Gravitational Lensing by Boson Stars
NASA Astrophysics Data System (ADS)
Boson stars can be gravitational lenses in a similar way as other astrophysical objects (Dabrowski & Schunck 2000). They can be transparent which allows the light to pass through them and to be gravitationally deflected. We discuss the lens equation for these stars as well as the details of magnification assuming they are on non-cosmological distance from the observer and that their mass is M = 1010M?. We find that there are typically three images of a star. There is one tangential critical curve (Einstein ring) and one radial critical curve for tangential and radial magnification, respectively. The deflection angles for the light moving in the gravitational field of boson stars can be very large (even of the order of degrees) which means that they are very strong relativistic objects. We derive an analytic formula for the lens equation applied for such large deflection angles. Although the large deflection angle images are highly demagnified, their existence in the area of the tangential critical curve may help in observational detection of suitable lenses possessing characteristic features of boson stars which could serve as a direct evidence for scalar fields in the universe...
Schunck, Franz E.; Dabrowski, Mariusz P.
Natural wormholes as gravitational lenses
Once quantum mechanical effects are included, the hypotheses underlying the positive mass theorem of classical general relativity fail. As an example of the peculiarities attendant upon this observation, a wormhole mouth embedded in a region of high mass density might accrete mass, giving the other mouth a net [ital negative] mass of unusual gravitational properties. The lensing of such a gravitationally negative anomalous compact halo object (GNACHO) will enhance background stars with a time profile that is observable and qualitatively different from that recently observed for massive compact halo objects (MACHO's) of positive mass. While the analysis is discussed in terms of wormholes, the observational test proposed is more generally a search for compact negative mass objects of any origin. We recommend that MACHO search data be analyzed for GNACHO's.
Cramer, J.G.; Forward, R.L.; Morris, M.S.; Visser, M.; Benford, G.; Landis, G.A. (Department of Physics, FM-15, University of Washington, Seattle, Washington 98195 (United States) Forward Unlimited, P.O. Box 2783, Malibu, California 90265 (United States) Department of Physics and Astronomy, Butler University, Indianapolis, Indiana 46208 (United States) Physics Department, Washington University, St. Louis, Missouri 63130-4899 (United States) Physics Department, University of California at Irvine, Irvine, California 92717-4575 (United States) NASA Lewis Research Center, Mail Code 302-1, Cleveland, Ohio 44135-3191 (United States))
Cosmology from weak lensing of CMB
NASA Astrophysics Data System (ADS)
The weak lensing effect on the cosmic microwave background (CMB) induces distortions in the spatial pattern of CMB anisotropies, and statistical properties of CMB anisotropies become a weakly non-Gaussian field. We first summarize the weak lensing effect on the CMB (CMB lensing) in the presence of scalar, vector, and tensor perturbations. Then we focus on the lensing effect on CMB statistics and methods to estimate deflection angles and their power spectrum. We end by summarizing recent observational progress and future prospects.
Namikawa, Toshiya
Gravitational lensing by rotating naked singularities
We model massive compact objects in galactic nuclei as stationary, axially symmetric naked singularities in the Einstein-massless scalar field theory and study the resulting gravitational lensing. In the weak deflection limit we study analytically the position of the two weak field images, the corresponding signed and absolute magnifications as well as the centroid up to post-Newtonian order. We show that there are static post-Newtonian corrections to the signed magnification and their sum as well as to the critical curves, which are functions of the scalar charge. The shift of the critical curves as a function of the lens angular momentum is found, and it is shown that they decrease slightly for the weakly naked and vastly for the strongly naked singularities with the increase of the scalar charge. The pointlike caustics drift away from the optical axis and do not depend on the scalar charge. In the strong deflection limit approximation, we compute numerically the position of the relativistic images and their separability for weakly naked singularities. All of the lensing quantities are compared to particular cases as Schwarzschild and Kerr black holes as well as Janis-Newman-Winicour naked singularities.
Gyulchev, Galin N. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria); Yazadjiev, Stoytcho S. [Department of Theoretical Physics, Faculty of Physics, Sofia University, 5 James Bourchier Boulevard, 1164 Sofia (Bulgaria); Institut fuer Theoretische Physik, Universitaet Goettingen, Friedrich-Hund-Platz 1, D-37077 Goettingen (Germany)
Investigations of Galaxy Clusters Using Gravitational Lensing
NASA Astrophysics Data System (ADS)
In this dissertation talk I describe my studies of galaxy clustering and gravitational lensing; both are important phenomena which can be used to study the structure and evolution of the universe. First I describe a sample of ten strong-lensing galaxy clusters of mass between 1-30x1014 h-1M?. These clusters were found in the Sloan Digital Sky Survey and were further observed using the WIYN 3.5-m telescope at Kitt Peak National Observatory and the Astrophysical Research Consortium 3.5-m telescope at Apache Point Observatory. Analyses of these clusters showed that the four lowest mass clusters in this sample exhibit overconcentration, that is, the concentration of mass in the centers of the clusters was higher than theory would predict. Second, I describe lens models of three of the strong lenses in this sample using a Bayesian algorithm for lens modeling. Finally I describe measurements of a mass-richness relation for galaxy clusters found at higher median redshift (z?0.6) than has been typical of previous sky surveys. This relation empirically describes how the mass of galaxy clusters is related to the number of galaxies in the cluster. Mass-richness calibration is a key component of cosmology analyses using galaxy clusters; thus this work will be important to studies of cosmology done with this decade's large sky surveys. Galaxy clusters were found using a Voronoi Tessellation cluster finder and masses were measured using stacked weak lensing shear measurements in bins of similar richness. The mass-richness relation was derived using data from the Blanco Cosmology Survey and from the Sloan Digital Sky Survey Stripe 82 coadd, leading to a sample of clusters covering a total sky area of about 400 square degrees.
Wiesner, Matthew P.; Lin, H.; Soares-Santos, M.
Defining a weak lensing experiment in space
NASA Astrophysics Data System (ADS)
This paper describes the definition of a typical next-generation space-based weak gravitational lensing experiment. We first adopt a set of top-level science requirements from the literature, based on the scale and depth of the galaxy sample, and the avoidance of systematic effects in the measurements which would bias the derived shear values. We then identify and categorize the contributing factors to the systematic effects, combining them with the correct weighting, in such a way as to fit within the top-level requirements. We present techniques which permit the performance to be evaluated and explore the limits at which the contributing factors can be managed. Besides the modelling biases resulting from the use of weighted moments, the main contributing factors are the reconstruction of the instrument point spread function, which is derived from the stellar images on the image, and the correction of the charge transfer inefficiency in the CCD detectors caused by radiation damage.
Cropper, Mark; Hoekstra, Henk; Kitching, Thomas; Massey, Richard; Amiaux, J�r�me; Miller, Lance; Mellier, Yannick; Rhodes, Jason; Rowe, Barnaby; Pires, Sandrine; Saxton, Curtis; Scaramella, Roberto
New stochastic approach to cumulative weak lensing
NASA Astrophysics Data System (ADS)
We study the weak gravitational lensing effects caused by a stochastic distribution of dark matter halos. We develop a simple approach to calculate the magnification probability distribution function which allows us to easily compute the magnitude bias and dispersion for an arbitrary data sample and a given universe model. As an application we consider the effects of single-mass large-scale cosmic inhomogeneities (M�1015h-1M?) to the SNe magnitude-redshift relation, and conclude that such structures could bias the PDF enough to affect the extraction of cosmological parameters from the limited size of present-day SNe data samples. We also release turboGL [turboGL is available at: http://www.turbogl.org.], a simple and very fast (?1s) Mathematica code based on the method here presented.
Kainulainen, Kimmo; Marra, Valerio
The Sloan Nearby Cluster Weak Lensing Survey
We describe and present initial results of a weak lensing survey of nearby (z lsim 0.1) galaxy clusters in the Sloan Digital Sky Survey (SDSS). In this first study, galaxy clusters are selected from the SDSS spectroscopic galaxy cluster catalogs of Miller et al. and Berlind et al. We report a total of seven individual low-redshift cluster weak lensing measurements
Jeffrey M. Kubo; James T. Annis; Frances Mei Hardin; Donna Kubik; Kelsey Lawhorn; Huan Lin; Liana Nicklaus; Dylan Nelson; Ribamar Rondon de Rezende Reis; Hee-Jong Seo; Marcelle Soares-Santos; Albert Stebbins; Tony Yunker
Surveying for Mass via Weak Lensing
NASA Astrophysics Data System (ADS)
Wide-field CCD mosaics on large telescopes now allow for direct surveys for mass concentrations. Weak gravitational lensing of the ~ 60 faint background galaxies per square arcminute creates a shear distortion pattern which can be transformed into a map of projected mass density. In a pilot survey using the Big Throughput Camera on the Blanco 4m telescope at CTIO, we have discovered several clusters of galaxies via this technique of gravitational lens mass tomography. Free of baryon bias, this new view of the universe will permit direct tests of the predictions of cosmological models. We show a color mural of one of our ``blank" fields for which we have deep images in several bands. 150,000 distant galaxies are seen in a half-degree field. Using the stars in the field to correct for low level shear systematics, we measure the shear induced by foreground mass concentrations at redshifts 0.2-0.6. The resulting mass map is shown. A large scale imaging survey of this kind would measure for the first time the change in large scale structure from z=1 to the present epoch, and test the current theories of structure formation, which predict that mass in the low-redshift Universe has a particular filamentary/sheetlike structure. These unique observations will constrain the clustering properties of matter, most notably Omega_matter and Omega_ Lambda , and, when compared with the results from microwave background anisotropy missions, will test the basic theory of structure formation via gravitational instability.
Tyson, J. A.; dell'Antonio, I. P.; Wittman, D.; Kirkman, D.; Bernstein, G.
Weak Lensing with Galaxy Kinematics
NASA Astrophysics Data System (ADS)
Weak lensing is weak because the shear signal is much smaller than the noise set by the broad distribution of intrinsic galaxy shapes. We describe a technique that can reduce shape noise by an order of magnitude using spatially-resolved spectroscopy to derive kinematic maps of source galaxies. Shear oriented along the principle axes of a rotating disk induces an offset from the Tully-Fisher relation after inclination corrections, while shear applied at an angle to the disk skews the kinematic axes relative to the photometric axes. Existing multi-object optical spectrographs and IFUs have the spatial and spectral resolution to measure this effect at high signal-to-noise. We discuss science applications ranging from high resolution cluster mass mapping to cosmic shear, including the statistical and systematic uncertainties which can be competitive with and complementary to traditional shear surveys. Notably, the need for photometric redshifts is eliminated, while biases due to shear calibration and intrinsic alignments can be significantly reduced.
George, Matthew R.; Huff, E. M.; Schlegel, D. J.
Using Galaxies to Understand Weak Lensing
NASA Astrophysics Data System (ADS)
While weak lensing measurements can provide a useful probe of galaxy-scale physics, it is not commonly appreciated that an understanding of galaxy-scale physics can in turn be used to dramatically improve weak lensing measurements. I will explain how galaxy scaling relations can enhance the weak lensing signal, and show recent results from a lensing magnification measurement using data from the Sloan Digital Sky Survey. The combination of magnification and shear measurements enabled by these techniques will permit significantly better weak lensing constraints on the distribution of mass on galaxy scales, in time for the newest generation of large, high-precision imaging surveys such as the Dark Energy Survey. I also discuss projections of what DES will be able to accomplish on this front.
Huff, Eric M.
The Sloan Nearby Cluster Weak Lensing Survey
We describe and present initial results of a weak lensing survey of nearby (z {approx}< 0.1) galaxy clusters in the Sloan Digital Sky Survey (SDSS). In this first study, galaxy clusters are selected from the SDSS spectroscopic galaxy cluster catalogs of Miller et al. and Berlind et al. We report a total of seven individual low-redshift cluster weak lensing measurements that include A2048, A1767, A2244, A1066, A2199, and two clusters specifically identified with the C4 algorithm. Our program of weak lensing of nearby galaxy clusters in the SDSS will eventually reach {approx}200 clusters, making it the largest weak lensing survey of individual galaxy clusters to date.
Kubo, Jeffrey M.; /Fermilab; Annis, James T.; /Fermilab; Hardin, Frances Mei; /Illinois Math. Sci. Acad.; Kubik, Donna; /Fermilab; Lawhorn, Kelsey; /Illinois Math. Sci. Acad.; Lin, Huan; /Fermilab; Nicklaus, Liana; /Illinois Math. Sci. Acad.; Nelson, Dylan; /UC, Berkeley; Reis, Ribamar Rondon de Rezende; /Fermilab; Seo, Hee-Jong; /Fermilab; Soares-Santos, Marcelle; /Fermilab /Inst. Geo. Astron., Havana /Sao Paulo U. /Fermilab
Weak lensing analysis in three dimensions
NASA Astrophysics Data System (ADS)
We present a comprehensive full-sky 3-dimensional analysis of the weak lensing fields and their corresponding power spectra. Using the formalism of spin-weight spherical harmonics and spherical Bessel functions, we relate the two-point statistics of the harmonic expansion coefficients of the weak lensing shear and convergence to the power spectrum of the matter density perturbations, and derive small-angle limits. Such a study is relevant in view of the next generation of large-scale weak lensing surveys which will provide distance information about the sources through photometric redshifts. This opens up the possibility of accurate cosmological parameter estimation via weak lensing, with an emphasis on the equation of state of dark energy.
Castro, P. G.; Heavens, A. F.; Kitching, T. D.
Magnified Weak Lensing Cross Correlation Tomography
This project carried out a weak lensing tomography (WLT) measurement around rich clusters of galaxies. This project used ground based photometric redshift data combined with HST archived cluster images that provide the WLT and cluster mass modeling. The technique has already produced interesting results (Guennou et al, 2010,Astronomy & Astrophysics Vol 523, page 21, and Clowe et al, 2011 to be submitted). Guennou et al have validated that the necessary accuracy can be achieved with photometric redshifts for our purposes. Clowe et al titled "The DAFT/FADA survey. II. Tomographic weak lensing signal from 10 high redshift clusters," have shown that for the **first time** via this purely geometrical technique, which does not assume a standard rod or candle, that a cosmological constant is **required** for flat cosmologies. The intent of this project is not to produce the best constraint on the value of the dark energy equation of state, w. Rather, this project is to carry out a sustained effort of weak lensing tomography that will naturally feed into the near term Dark Energy Survey (DES) and to provide invaluable mass calibration for that project. These results will greatly advance a key cosmological method which will be applied to the top-rated ground-based project in the Astro2020 decadal survey, LSST. Weak lensing tomography is one of the key science drivers behind LSST. CO-I Clowe is on the weak lensing LSST committee, and senior scientist on this project, at FNAL James Annis, plays a leading role in the DES. This project has built on successful proposals to obtain ground-based imaging for the cluster sample. By 1 Jan, it is anticipated the project will have accumulated complete 5-color photometry on 30 (or about 1/3) of the targeted cluster sample (public webpage for the survey is available at http://cencos.oamp.fr/DAFT/ and has a current summary of the observational status of various clusters). In all, the project has now been awarded the equivalent of over 60 nights on 4-m class telescopes, which gives concrete evidence of strong community support for this project. The WLT technique is based on the dependence of the gravitational shear signal on the angular diameter distances between the observer, the lens, and the lensed galaxy to measure cosmological parameters. By taking the ratio of measured shears of galaxies with different redshifts around the same lens, one obtains a measurement of the ratios of the angular diameter distances involved. Making these observations over a large range of lenses and background galaxy redshifts will measure the history of the expansion rate of the universe. Because this is a purely geometric measurement, it is insensitive to any form of evolution of objects or the necessity to understand the physics in the early universe. Thus, WLT was identified by the Dark Energy Task Force as perhaps the best method to measure the evolution of DE. To date, however, the conjecture of the DETF has not been experimentally verified, but will be by the proposed project. The primary reason for the lack of tomography measurements is that one must have an exceptional data-set to attempt the measurement. One needs both extremely good seeing (or space observations) in order to minimize the point spread function smearing corrections on weak lensing shear measurements and deep, multi-color data, from B to z, to measure reliable photometric redshifts of the background galaxies being lensed (which are typically too faint to obtain spectroscopic redshifts). Because the entire process from multi-drizzling the HST images, and then creating shear maps, to gathering the necessary ground based observations, to generating photo-zs and then carrying out the tomography is a complicated task, until the creation of our team, nobody has taken the time to connect all the levels of expertise necessary to carry out this project based on HST archival data. Our data are being used in 2 Ph.D. theses. Kellen Murphy, at Ohio University, is using the tomography data along with simulations in a thesis expected to be completed in Jun
Ulmer, Melville P., Clowe, Douglas I.
Weak lensing analysis in three dimensions
We present a comprehensive full-sky 3-dimensional analysis of the weak lensing fields and their corresponding power spectra. Using the formalism of spin-weight spherical harmonics and spherical Bessel functions, we relate the two-point statistics of the harmonic expansion coefficients of the weak lensing shear and convergence to the power spectrum of the matter density perturbations, and derive small-angle limits. Such a
P. G. Castro; A. F. Heavens; T. D. Kitching
Lognormal Property of Weak Lensing Fields
The statistical properties of weak-lensing fields are studied quantitatively using ray-tracing simulations. Motivated by an empirical lognormal model that excellently characterizes the probability distribution function of a three-dimensional mass distribution, we critically investigate the validity of the lognormal model in weak-lensing statistics. Assuming that the convergence field kappa is approximately described by the lognormal distribution, we present analytic formulae of
Atsushi Taruya; Masahiro Takada; Takashi Hamana; Issha Kayo; Toshifumi Futamase
Weak Lensing: Dark Matter, Dark Energy
The light rays from distant galaxies are deflected by massive structures along the line of sight, causing the galaxy images to be distorted.Measurements of these distortions, known as weak lensing, provide a way of measuring the distribution of dark matter as well as the spatial geometry of the universe. I will describe the ideas underlying this approach to cosmology. With planned large imaging surveys, weak lensing is a powerful probe of dark energy. I will discuss the observational challenges ahead and recent progress in developing multiple, complementary approaches to lensing measurements.
Weak Lensing: Dark Matter, Dark Energy
The light rays from distant galaxies are deflected by massive structures along the line of sight, causing the galaxy images to be distorted. Measurements of these distortions, known as weak lensing, provide a way of measuring the distribution of dark matter as well as the spatial geometry of the universe. I will describe the ideas underlying this approach to cosmology. With planned large imaging surveys, weak lensing is a powerful probe of dark energy. I will discuss the observational challenges ahead and recent progress in developing multiple, complementary approaches to lensing measurements.
Weak Lensing: Dark Matter, Dark Energy
The light rays from distant galaxies are deflected by massive structures along the line of sight, causing the galaxy images to be distorted.Measurements of these distortions, known as weak lensing, provide a way of measuring the distribution of dark matter as well as the spatial geometry of the universe. I will describe the ideas underlying this approach to cosmology. With planned large imaging surveys, weak lensing is a powerful probe of dark energy. I will discuss the observational challenges ahead and recent progress in developing multiple, complementary approaches to lensing measurements.
Bhuvnesh Jain
The conceptual origins of gravitational lensing
NASA Astrophysics Data System (ADS)
We critically examine the evidence available of the early ideas on the bending of light due to a gravitational attraction, which led to the concept of gravitational lenses, and attempt to present an undistorted historical perspective. Contrary to a widespread but baseless claim, Newton was not the precursor to the idea, and the first Query in his Opticks is totally unrelated to this phenomenon. We briefly review the roles of Voltaire, Marat, Cavendish, Soldner and Einstein in their attempts to quantify the gravitational deflection of light. The first, but unpublished, calculations of the lensing effect produced by this deflection are found in Einstein's 1912 notebooks, where he derived the lensing equation and the formation of images in a gravitational lens. The brief 1924 paper by Chwolson which presents, without calculations, the formation of double images and rings by a gravitational lens passed mostly unnoticed. The unjustly forgotten and true pioneer of the subject is F. Link, who not only published the first detailed lensing calculations in 1936, nine months prior to Einstein's famous paper in Science, but also extended the theory to include the effects of finite-size sources and lenses, binary sources, and limb darkening that same year. Link correctly predicted that the microlensing effect would be easier to observe in crowded fields or in galaxies, as observations confirmed five decades later. The calculations made by Link are far more detailed than those by Tikhov and Bogorodsky. We discuss briefly some papers of the early 1960s which marked the renaissance of this theoretical subject prior to the first detection of a gravitational lens in 1979, and we conclude with the unpublished chapter of Petrou's 1981 PhD thesis addressing the microlensing of stars in the Magellanic clouds by dark objects in the Galactic halo.
Valls-Gabaud, David
Sky masking is unavoidable in wide-field weak-lensing observations. We study how masks affect the measurement of statistics of matter distribution probed by weak gravitational lensing. We first use 1000 cosmological ray-tracing simulations to examine in detail the impact of masked regions on the weak-lensing Minkowski Functionals (MFs). We consider actual sky masks used for a Subaru Suprime-Cam imaging survey. The masks increase the variance of the convergence field and the expected values of the MFs are biased. The bias then compromises the non-Gaussian signals induced by the gravitational growth of structure. We then explore how masks affect cosmological parameter estimation. We calculate the cumulative signal-to-noise ratio (S/N) for masked maps to study the information content of lensing MFs. We show that the degradation of S/N for masked maps is mainly determined by the effective survey area. We also perform simple {chi}{sup 2} analysis to show the impact of lensing MF bias due to masked regions. Finally, we compare ray-tracing simulations with data from a Subaru 2 deg{sup 2} survey in order to address if the observed lensing MFs are consistent with those of the standard cosmology. The resulting {chi}{sup 2}/n{sub dof} = 29.6/30 for three combined MFs, obtained with the mask effects taken into account, suggests that the observational data are indeed consistent with the standard {Lambda}CDM model. We conclude that the lensing MFs are a powerful probe of cosmology only if mask effects are correctly taken into account.
Shirasaki, Masato; Yoshida, Naoki [Department of Physics, University of Tokyo, Tokyo 113-0033 (Japan); Hamana, Takashi, E-mail: firstname.lastname@example.com [National Astronomical Observatory of Japan, Tokyo 181-0015 (Japan)
Effect of Masked Regions on Weak-lensing Statistics
NASA Astrophysics Data System (ADS)
Sky masking is unavoidable in wide-field weak-lensing observations. We study how masks affect the measurement of statistics of matter distribution probed by weak gravitational lensing. We first use 1000 cosmological ray-tracing simulations to examine in detail the impact of masked regions on the weak-lensing Minkowski Functionals (MFs). We consider actual sky masks used for a Subaru Suprime-Cam imaging survey. The masks increase the variance of the convergence field and the expected values of the MFs are biased. The bias then compromises the non-Gaussian signals induced by the gravitational growth of structure. We then explore how masks affect cosmological parameter estimation. We calculate the cumulative signal-to-noise ratio (S/N) for masked maps to study the information content of lensing MFs. We show that the degradation of S/N for masked maps is mainly determined by the effective survey area. We also perform simple ?2 analysis to show the impact of lensing MF bias due to masked regions. Finally, we compare ray-tracing simulations with data from a Subaru 2 deg2 survey in order to address if the observed lensing MFs are consistent with those of the standard cosmology. The resulting ?2/n dof = 29.6/30 for three combined MFs, obtained with the mask effects taken into account, suggests that the observational data are indeed consistent with the standard ?CDM model. We conclude that the lensing MFs are a powerful probe of cosmology only if mask effects are correctly taken into account.
Shirasaki, Masato; Yoshida, Naoki; Hamana, Takashi
Galilean-invariant scalar fields can strengthen gravitational lensing.
The mystery of dark energy suggests that there is new gravitational physics on long length scales. Yet light degrees of freedom in gravity are strictly limited by Solar System observations. We can resolve this apparent contradiction by adding a Galilean-invariant scalar field to gravity. Called Galileons, these scalars have strong self-interactions near overdensities, like the Solar System, that suppress their dynamical effect. These nonlinearities are weak on cosmological scales, permitting new physics to operate. In this Letter, we point out that a massive-gravity-inspired coupling of Galileons to stress energy can enhance gravitational lensing. Because the enhancement appears at a fixed scaled location for dark matter halos of a wide range of masses, stacked cluster analysis of weak lensing data should be able to detect or constrain this effect. PMID:21668215
Wyman, Mark
Gravitational Lensing of Supernova Neutrinos
The black hole at the center of the galaxy is a powerful lens for supernova neutrinos. In the very special circumstance of a supernova near the extended line of sight from Earth to the galactic center, lensing could dramatically enhance the neutrino flux at Earth and stretch the neutrino pulse.
Mena, Olga; /Fermilab /Rome U.; Mocioiu, Irina; /Penn State U.; Quigg, Chris; /Fermilab
Kinematic Weak Lensing: Forecasts for a Next-Generation Lensing Measurement
NASA Astrophysics Data System (ADS)
Weak gravitational lensing by cosmic structure is a major science driver for several large ongoing and planned imaging surveys, such as the Dark Energy Survey and the Euclid space mission. Traditionally, lensing in this regime is measured via statistical distortions to the shapes of galaxies. While the cosmological constraining power for a large imaging survey employing this technique is great, the signal itself is noisy, and susceptible to a number of systematic biases. Here we propose a new lensing technique that makes use of the kinematics of disk galaxies and the Tully-Fisher relation. Our method controls for that part of the shape noise which arises from the random orientation of galaxy disks, and promises an increase in signal-to-noise sufficient to bring weak lensing measurements within the reach of the next generation of spectroscopic surveys. We define such a survey here, discuss the advantages and disadvantages, and show that the cosmological constraining power of this kinematic weak lensing method is competitive with the most powerful planned lensing measurements.
Huff, Eric M.; George, M. R.; Krause, E.; Eifler, T.; Schlegel, D. J.
Relationship between high-energy absorption cross section and strong gravitational lensing for black hole
NASA Astrophysics Data System (ADS)
In this paper, we obtain a relation between the high-energy absorption cross section and the strong gravitational lensing for a static and spherically symmetric black hole. It provides us a possible way to measure the high-energy absorption cross section for a black hole from strong gravitational lensing through astronomical observation. More importantly, it allows us to compute the total energy emission rate for high-energy particles emitted from the black hole acting as a gravitational lens. It could tell us the range of the frequency, among which the black hole emits the most of its energy and the gravitational waves are most likely to be observed. We also apply it to the Janis-Newman-Winicour solution. The results suggest that we can test the cosmic censorship hypothesis through the observation of gravitational lensing by the weakly naked singularities acting as gravitational lenses.
Wei, Shao-Wen; Liu, Yu-Xiao; Guo, Heng
Strong gravitational lensing of gravitational waves in Einstein Telescope
NASA Astrophysics Data System (ADS)
Gravitational wave experiments have entered a new stage which gets us closer to the opening a new observational window on the Universe. In particular, the Einstein Telescope (ET) is designed to have a fantastic sensitivity that will provide with tens or hundreds of thousand NS-NS inspiral events per year up to the redshift z = 2. Some of such events should be gravitationally lensed by intervening galaxies. We explore the prospects of observing gravitationally lensed inspiral NS-NS events in the Einstein telescope. Being conservative we consider the lens population of elliptical galaxies. It turns out that depending on the local insipral rate ET should detect from one per decade detection in the pessimistic case to a tens of detections per year for the most optimistic case. The detection of gravitationally lensed source in gravitational wave detectors would be an invaluable source of information concerning cosmography, complementary to standard ones (like supernovae or BAO) independent of the local cosmic distance ladder calibrations.
Pi�rkowska, Aleksandra; Biesiada, Marek; Zhu, Zong-Hong
First measurement of gravitational lensing by cosmic voids in SDSS
NASA Astrophysics Data System (ADS)
We report the first measurement of the diminutive lensing signal arising from matter underdensities associated with cosmic voids. While undetectable individually, by stacking the weak gravitational shear estimates around 901 voids detected in Sloan Digital Sky Survey DR7 by Sutter et al., we find substantial evidence for a depression of the lensing signal compared to the cosmic mean. This depression is most pronounced at the void radius, in agreement with analytical models of void matter profiles. Even with the largest void sample and imaging survey available today, we cannot put useful constraints on the radial dark matter void profile. We invite independent investigations of our findings by releasing data and analysis code to the public at https://github.com/pmelchior/void-lensing.
Melchior, Peter; Sutter, P. M.; Sheldon, Erin S.; Krause, Elisabeth; Wandelt, Benjamin D.
Weak Lensing Measurements: A Revisited Method and Application toHubble Space Telescope Images
The weak distortions produced by gravitational lensing in the images of background galaxies provide a unique method to measure directly the distribution of mass in the universe. However, because the induced distortions are only of a few percent, this technique requires high-precision measurements of the lensing shear and cautious corrections for systematic effects. Kaiser, Squires, & Broadhurst proposed a method
Jason Rhodes; Alexandre Refregier; Edward J. Groth
I. Ash ejection and exposure during radius expansion type I X-ray bursts, II. Stellar dynamics at the galactic center, III. Weak gravitational lensing by dark matter concentrations
NASA Astrophysics Data System (ADS)
The studies presented herein are on three distinct topics in astrophysics: I. We solve for the evolution of the vertical extent of the convective region of a neutron star atmosphere during a type I X-ray burst. The convective region is well-mixed with ashes of nuclear burning, and its extent determines the burst rise time. We show that the maximum extent of the convective region during photospheric radius expansion (PRE) bursts can be sufficiently great that some ashes of burning are: (1) ejected by the radiation-driven wind during the PRE phase and, (2) exposed at the neutron star surface following the PRE phase. We calculate the expected column density of ashes in hydrogen-like states and find that the resulting photoionization edges should be detectable with current high spectral resolution X-ray telescopes. A detection would probe the burst nuclear burning processes and might enable a measurement of the neutron star gravitational redshift. II. We discuss physical experiments achievable via the monitoring of stellar dynamics near the massive black hole (MBH) at the Galactic center with a next- generation, extremely large telescope (ELT). We use the Markov Chain Monte Carlo method to evaluate the constraints that the monitoring of these orbits will place on the matter content at the Galactic center. We compare these future constraints with those obtained with the current data. We also describe how the monitoring of stellar proper motions can be used to probe directly the masses of isolated stellar remnants near the MBH. III. We calculate the abundance of dark-matter concentrations that are sufficiently overdense to produce a detectable weak-gravitational-lensing signal. Most of these overdensities are virialized halos containing identifiable X-ray and/or optical clusters. However, a significant fraction are nonvirialized, cluster-mass overdensities still in the process of gravitational collapse---these should produce significantly weaker or no X-ray emission. Our predicted abundance of such dark clusters is consistent with the abundance implied by the detection of apparent dark lenses. We also examine the prospect of using weak gravitational lenses to constrain the dark energy equation-of- state.
Weinberg, Nevin Nachum
Invariants of simple gravitational lenses
NASA Astrophysics Data System (ADS)
We present approximate tests which can be applied to a newly observed quadruple QSO, or to a quadruplet of extended objects distorted by a foreground cluster of galaxies. These tests indicate whether the responsible gravitational lens may have a simple mass distribution. If the lens galaxy is detected, the tests give an approximate orientation for it, which can be compared with the observed orientation of the galaxy. The tests do not require construction of an explicit lens model, and therefore can save time and effort. In the case of many objects distorted by a cluster, these diagnostics can help to select possible quadruplet candidates.
Kassiola, Aggeliki; Kovner, Israel
Subaru Weak Lensing Measurements of Four Strong Lensing Clusters: Are Lensing Clusters Over-Concentrated?
We derive radial mass profiles of four strong lensing selected clusters which show prominent giant arcs (Abell 1703, SDSS J1446+3032, SDSS J1531+3414, and SDSS J2111-0115), by combining detailed strong lens modeling with weak lensing shear measured from deep Subaru Suprime-cam images. Weak lensing signals are detected at high significance for all four clusters, whose redshifts range from z = 0.28 to 0.64. We demonstrate that adding strong lensing information with known arc redshifts significantly improves constraints on the mass density profile, compared to those obtained from weak lensing alone. While the mass profiles are well fitted by the universal form predicted in N-body simulations of the {Lambda}-dominated cold dark matter model, all four clusters appear to be slightly more centrally concentrated (the concentration parameters c{sub vir} {approx} 8) than theoretical predictions, even after accounting for the bias toward higher concentrations inherent in lensing selected samples. Our results are consistent with previous studies which similarly detected a concentration excess, and increases the total number of clusters studied with the combined strong and weak lensing technique to ten. Combining our sample with previous work, we find that clusters with larger Einstein radii are more anomalously concentrated. We also present a detailed model of the lensing cluster Abell 1703 with constraints from multiple image families, and find the dark matter inner density profile to be cuspy with the slope consistent with -1, in agreement with expectations.
Oguri, Masamune; Hennawi, Joseph F.; Gladders, Michael D.; Dahle, Haakon; Natarajan, Priyamvada; Dalal, Neal; Koester, Benjamin P.; Sharon, Keren; Bayliss, Matthew
The Third Gravitational Lensing Accuracy Testing (GREAT3) Challenge Handbook
NASA Astrophysics Data System (ADS)
The GRavitational lEnsing Accuracy Testing 3 (GREAT3) challenge is the third in a series of image analysis challenges, with a goal of testing and facilitating the development of methods for analyzing astronomical images that will be used to measure weak gravitational lensing. This measurement requires extremely precise estimation of very small galaxy shape distortions, in the presence of far larger intrinsic galaxy shapes and distortions due to the blurring kernel caused by the atmosphere, telescope optics, and instrumental effects. The GREAT3 challenge is posed to the astronomy, machine learning, and statistics communities, and includes tests of three specific effects that are of immediate relevance to upcoming weak lensing surveys, two of which have never been tested in a community challenge before. These effects include many novel aspects including realistically complex galaxy models based on high-resolution imaging from space; a spatially varying, physically motivated blurring kernel; and a combination of multiple different exposures. To facilitate entry by people new to the field, and for use as a diagnostic tool, the simulation software for the challenge is publicly available, though the exact parameters used for the challenge are blinded. Sample scripts to analyze the challenge data using existing methods will also be provided. See http://great3challenge.info and http://great3.projects.phys.ucl.ac.uk/leaderboard/ for more information.
Mandelbaum, Rachel; Rowe, Barnaby; Bosch, James; Chang, Chihway; Courbin, Frederic; Gill, Mandeep; Jarvis, Mike; Kannawadi, Arun; Kacprzak, Tomasz; Lackner, Claire; Leauthaud, Alexie; Miyatake, Hironao; Nakajima, Reiko; Rhodes, Jason; Simet, Melanie; Zuntz, Joe; Armstrong, Bob; Bridle, Sarah; Coupon, Jean; Dietrich, J�rg P.; Gentile, Marc; Heymans, Catherine; Jurling, Alden S.; Kent, Stephen M.; Kirkby, David; Margala, Daniel; Massey, Richard; Melchior, Peter; Peterson, John; Roodman, Aaron; Schrabback, Tim
Profiles of a Key Programme: Gravitational Lensing
NASA Astrophysics Data System (ADS)
Prior to Professor van der Laan's enquiry, in the March 1988 issue of the Messenger, on the general interest among astronomers from the European community to possibly participate in Key Programmes (KPs) at the European 80uthern Observatory, at least three distinct groups (including more than half of the above authors) were already involved in the study of "gravitational lensing" effects (see box on pages 10-11). Observations were being performed with the help of various telescopes on La 8illa as weil as at other observatories (VLA, CFHT, Palomar, Kitt Peak, etc.).
Surdej, J.; Arnaud, J.; Borgeest, U.; Djorgovski, S.; Fleischmann, F.; Hammer, F.; Hutsemekers, D.; Kayser, R.; Le Fevre, O.; Nottale, L.; Magain, P.; Meylan, G.; Refsdal, S.; Remy, M.; Shaver, P.; Smette, A.; Swings, J. P.; Vanderriest, C.; van Drom, E.; V�ron-Cetty, M.; V�ron, P.; Weigelt, G.
Time delay and magnification centroid due to gravitational lensing by black holes and naked singularities
We model the massive dark object at the center of the Galaxy as a Schwarzschild black hole as well as Janis-Newman-Winicour naked singularities, characterized by the mass and scalar charge parameters, and study gravitational lensing (particularly time delay, magnification centroid, and total magnification) by them. We find that the lensing features are qualitatively similar (though quantitatively different) for Schwarzschild black holes, weakly naked, and marginally strongly naked singularities. However, the lensing characteristics of strongly naked singularities are qualitatively very different from those due to Schwarzschild black holes. The images produced by Schwarzschild black hole lenses and weakly naked and marginally strongly naked singularity lenses always have positive time delays. On the other hand, strongly naked singularity lenses can give rise to images with positive, zero, or negative time delays. In particular, for a large angular source position the direct image (the outermost image on the same side as the source) due to strongly naked singularity lensing always has a negative time delay. We also found that the scalar field decreases the time delay and increases the total magnification of images; this result could have important implications for cosmology. As the Janis-Newman-Winicour metric also describes the exterior gravitational field of a scalar star, naked singularities as well as scalar star lenses, if these exist in nature, will serve as more efficient cosmic telescopes than regular gravitational lenses.
Virbhadra, K. S.; Keeton, C. R. [Department of Mathematics, Physics and Statistics, University of the Sciences in Philadelphia, Philadelphia, PA 19104 (United States); Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States)
Point mass deflectors in gravitational lenses
NASA Technical Reports Server (NTRS)
The observed properties of the six systems generally accepted as gravitational lenses are compared with the properties predicted for the images of point-mass and distributed mass deflectors. Taken as a statistical distribution, the characteristics of the six known systems strongly suggest the existence of a super-massive black hole as the effective deflecting mass in one or more of these systems. If the deflecting mass in a gravitational lens is a black hole, the distance to the deflecting mass can be determined directly from the difference in light travel time along the separate image paths. (No direct solution for the distance to the deflecting mass exists when the deflecting mass is a galaxy or a cluster of galaxies). Geometric parallaxes of objects at 1000 Mpc distance are of obvious importance in a wide variety of cosmological studies.
Dolan, Joseph F.
Thermal lensing in recycling interferometric gravitational wave detectors
Thermal lensing limits the performance of advanced interferometric gravitational wave detectors that use high light powers. We evaluate the effects of thermal lensing in such systems and estimate their gravitational wave sensitivity assuming that fused silica optical substrates are employed. Although useful sensitivity can be achieved with established designs, the new technique of resonant sideband extraction is most promising for
K. A. Strain; K. Danzmann; J. Mizuno; P. G. Nelson; A. R�diger; R. Schilling; W. Winkler
Spurious Shear in Weak Lensing with LSST
The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.
Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.
Three Gravitationally Lensed Supernovae behind CLASH Galaxy Clusters
NASA Astrophysics Data System (ADS)
We report observations of three gravitationally lensed supernovae (SNe) in the Cluster Lensing And Supernova survey with Hubble (CLASH) Multi-Cycle Treasury program. These objects, SN CLO12Car (z = 1.28), SN CLN12Did (z = 0.85), and SN CLA11Tib (z = 1.14), are located behind three different clusters, MACSJ1720.2+3536 (z = 0.391), RXJ1532.9+3021 (z = 0.345), and A383 (z = 0.187), respectively. Each SN was detected in Hubble Space Telescope optical and infrared images. Based on photometric classification, we find that SNe CLO12Car and CLN12Did are likely to be Type Ia supernovae (SNe Ia), while the classification of SN CLA11Tib is inconclusive. Using multi-color light-curve fits to determine a standardized SN Ia luminosity distance, we infer that SN CLO12Car was ~1.0 � 0.2 mag brighter than field SNe Ia at a similar redshift and ascribe this to gravitational lens magnification. Similarly, SN CLN12Did is ~0.2 � 0.2 mag brighter than field SNe Ia. We derive independent estimates of the predicted magnification from CLASH strong+weak-lensing maps of the clusters (in magnitude units, 2.5 log10?): 0.83 � 0.16 mag for SN CLO12Car, 0.28 � 0.08 mag for SN CLN12Did, and 0.43 � 0.11 mag for SN CLA11Tib. The two SNe Ia provide a new test of the cluster lens model predictions: we find that the magnifications based on the SN Ia brightness and those predicted by the lens maps are consistent. Our results herald the promise of future observations of samples of cluster-lensed SNe Ia (from the ground or space) to help illuminate the dark-matter distribution in clusters of galaxies, through the direct determination of absolute magnifications.
Patel, Brandon; McCully, Curtis; Jha, Saurabh W.; Rodney, Steven A.; Jones, David O.; Graur, Or; Merten, Julian; Zitrin, Adi; Riess, Adam G.; Matheson, Thomas; Sako, Masao; Holoien, Thomas W.-S.; Postman, Marc; Coe, Dan; Bartelmann, Matthias; Balestra, Italo; Ben�tez, Narciso; Bouwens, Rychard; Bradley, Larry; Broadhurst, Tom; Cenko, S. Bradley; Donahue, Megan; Filippenko, Alexei V.; Ford, Holland; Garnavich, Peter; Grillo, Claudio; Infante, Leopoldo; Jouvel, St�phanie; Kelson, Daniel; Koekemoer, Anton; Lahav, Ofer; Lemze, Doron; Maoz, Dan; Medezinski, Elinor; Melchior, Peter; Meneghetti, Massimo; Molino, Alberto; Moustakas, John; Moustakas, Leonidas A.; Nonino, Mario; Rosati, Piero; Seitz, Stella; Strolger, Louis G.; Umetsu, Keiichi; Zheng, Wei
Strong field gravitational lensing in scalar tensor theories
NASA Astrophysics Data System (ADS)
Strong field gravitational lensing in the Brans Dicke scalar tensor theory has been studied. The deflection angle for photons passing very close to the photon sphere is estimated for the static spherically symmetric spacetime of the theory and the position and magnification of the relativistic images are obtained. Modelling the super massive central object of the galaxy by the Brans Dicke spacetime, numerical values of different strong lensing observables are estimated. It is found that against the expectation there is no significant scalar field effect on the strong field observable lensing parameters. This result raises question on the potentiality of strong field lensing to discriminate different gravitational theories.
Sarkar, Kabita; Bhadra, Arunava
Weak Lensing Measurements: A Revisited Method and Application to HST Images
The weak distortions produced by gravitational lensing in the images of\\u000abackground galaxies provide a method to measure directly the distribution of\\u000amass in the universe. However this technique requires high precision\\u000ameasurements of the lensing shear and cautious corrections for systematic\\u000aeffects. Kaiser, Squires, & Broadhurst (1995) proposed a method to calibrate\\u000athe ellipticity-shear relation in the presence of
Jason Rhodes; Alexandre Refregier; Ed Groth
Extreme gravitational lensing near rotating black holes
NASA Astrophysics Data System (ADS)
We describe a new approach to calculating photon trajectories and gravitational lensing effects in the strong gravitational field of the Kerr black hole. These techniques are applied to explore both the imaging and spectral properties of photons emitted from an accretion disc, which perform multiple orbits of the central mass before escaping to infinity. Viewed at large inclinations, these higher-order photons contribute ~20 per cent of the total luminosity of the system for a Schwarzschild hole, while for an extreme Kerr black hole this fraction rises to ~60 per cent. In more realistic models, these photons will be reabsorbed by the disc at large distances from the hole, but this returning radiation could provide a physical mechanism to resolve the discrepancy between the predicted and observed optical/ultraviolet colours in active galactic nuclei. Conversely, at low inclinations, higher-order images reintercept the disc plane close to the black hole, so need not be absorbed by the disc if this is within the plunging region. These photons form a bright ring carrying approximately 10 per cent of the total disc luminosity for a Schwarzschild black hole. The spatial separation between the inner edge of the disc and the ring is similar to the size of the event horizon. This is resolvable for supermassive black holes with proposed X-ray interferometery missions such as the Microarcsecond X-ray Imaging Mission (MAXIM), and so has the potential to provide an observational test of strong field gravity.
Beckwith, Kris; Done, Chris
Gravitational lensing with three-dimensional ray tracing
NASA Astrophysics Data System (ADS)
High-redshift sources suffer from magnification or demagnification due to weak gravitational lensing by large-scale structure. One consequence of this is that the distance-redshift relation, in wide use for cosmological tests, suffers lensing-induced scatter which can be quantified by the magnification probability distribution. Predicting this distribution generally requires a method for ray tracing through cosmological N-body simulations. However, standard methods tend to apply the multiple-thin-lens approximation. In an effort to quantify the accuracy of these methods, we develop an innovative code that performs ray tracing without the use of this approximation. The efficiency and accuracy of this computationally challenging approach can be improved by careful choices of numerical parameters; therefore, the results are analysed for the behaviour of the ray-tracing code in the vicinity of Schwarzschild and Navarro-Frenk-White lenses. Preliminary comparisons are drawn with the multiple-lens-plane ray-bundle method in the context of cosmological mass distributions for a source redshift of zs= 0.5. Research undertaken as part of the Commonwealth Cosmology Initiative (CCI: ), an international collaboration supported by the Australian Research Council (ARC).
Killedar, M.; Lasky, P. D.; Lewis, G. F.; Fluke, C. J.
Gravitational Lenses and the Structure and Evolution of Galaxies
NASA Technical Reports Server (NTRS)
This grant has supported papers which present a new direction in the theory and interpretation of gravitational lenses. During the second year we have focused more closely on the relationship of baryons and dark matter.
Kockanek, Christopher; Oliversen, Ronald J. (Technical Monitor)
What is Gravitational Lensing? (LBNL Summer Lecture Series)
Summer Lecture Series 2009: Gravitational lensing is explained by Einstein's general theory of relativity: galaxies and clusters of galaxies, which are very massive objects, act on spacetime by causing it to become curved. Alexie Leauthaud and Reiko Nakajima, astrophysicists with the Berkeley Center for Cosmological Physics, will discuss how scientists use gravitational lensing to investigate the nature of dark energy and dark matter in the universe.
Leauthaud, Alexie; Nakajima, Reiko [Berkeley Center for Cosmological Physics
GLIMPSE: accurate 3D weak lensing reconstructions using sparsity
NASA Astrophysics Data System (ADS)
We present GLIMPSE - Gravitational Lensing Inversion and MaPping with Sparse Estimators - a new algorithm to generate density reconstructions in three dimensions from photometric weak lensing measurements. This is an extension of earlier work in one dimension aimed at applying compressive sensing theory to the inversion of gravitational lensing measurements to recover 3D density maps. Using the assumption that the density can be represented sparsely in our chosen basis - 2D transverse wavelets and 1D line-of-sight Dirac functions - we show that clusters of galaxies can be identified and accurately localized and characterized using this method. Throughout, we use simulated data consistent with the quality currently attainable in large surveys. We present a thorough statistical analysis of the errors and biases in both the redshifts of detected structures and their amplitudes. The GLIMPSE method is able to produce reconstructions at significantly higher resolution than the input data; in this paper, we show reconstructions with 6 times finer redshift resolution than the shear data. Considering cluster simulations with 0.05 ? zcl ? 0.75 and 3 � 1013 ? Mvir ? 1015 h-1 M?, we show that the redshift extent of detected peaks is typically 1-2 pixel, or ?z ? 0.07, and that we are able to recover an unbiased estimator of the redshift of a detected cluster by considering many realizations of the noise. We also recover an accurate estimator of the mass, which is largely unbiased when the redshift is known and whose bias is constrained to ?5 per cent in the majority of our simulations when the estimated redshift is taken to be the true redshift. This shows a substantial improvement over earlier 3D inversion methods, which showed redshift smearing with a typical standard deviation of ? � 0.2-0.3, a significant damping of the amplitude of the peaks detected, and a bias in the detected redshift.
Leonard, Adrienne; Lanusse, Fran�ois; Starck, Jean-Luc
Effects of supermassive binary black holes on gravitational lenses
Recent observations indicate that many, if not all, galaxies host massive central black holes (BHs). In this paper, we explore the influence of supermassive binary black holes (SMBBHs) on their actions as gravitational lenses. When lenses are modelled as singular isothermal ellipsoids, binary BHs change the critical curves and caustics differently as a function of distance. Each BH can in
Nan Li; Shude Mao; Liang Gao; Abraham Loeb; R. di Stefano
Neutrino physics from future weak lensing surveys
NASA Astrophysics Data System (ADS)
Given recent indications of additional neutrino species and cosmologically significant neutrino masses, we analyze their signatures in the weak lensing shear power spectrum. We find that a shear deficit in the 20%-40% range or excess in the 20%-60% range cannot be explained by variations in parameters of the flat ?CDM model that are allowed by current observations of the expansion history from Type Ia supernovae, baryon acoustic oscillations, and local measures of the Hubble constant H0, coupled with observations of the cosmic microwave background from WMAP9 and the South Pole Telescope 2500 square degree survey. Hence such a shear deficit or excess would indicate large masses or extra species, respectively, and we find this to be independent of the flatness assumption. We also discuss the robustness of these predictions to cosmic acceleration physics and the means by which shear degeneracies in joint variation of mass and species can be broken.
Vanderveld, R. Ali; Hu, Wayne
COSMOS: Three-dimensional Weak Lensing and the Growth of Structure
We present a three-dimensional cosmic shear analysis of the Hubble Space Telescope COSMOS survey, the largest ever optical imaging program performed in space. We have measured the shapes of galaxies for the telltale distortions caused by weak gravitational lensing and traced the growth of that signal as a function of redshift. Using both 2D and 3D analyses, we measure cosmological
Richard Massey; Jason Rhodes; Alexie Leauthaud; Peter Capak; Richard Ellis; Anton Koekemoer; Alexandre R�fr�gier; Nick Scoville; James E. Taylor; Justin Albert; Joel Berg�; Catherine Heymans; David Johnston; Jean-Paul Kneib; Yannick Mellier; Bahram Mobasher; Elisabetta Semboloni; Patrick Shopbell; Lidia Tasca; Ludovic Van Waerbeke
The impact of high spatial frequency atmospheric distortions on weak lensing measurements
High precision cosmology with weak gravitational lensing requires a precise measure of the Point Spread Function across the imaging data where the accuracy to which high spatial frequency variation can be modelled is limited by the stellar number density across the field. We analyse dense stellar fields imaged at the Canada-France-Hawaii Telescope to quantify the degree of high spatial frequency
Catherine Heymans; Barnaby Rowe; Henk Hoekstra; Lance Miller; Thomas Erben; Thomas Kitching; Ludovic Van Waerbeke
Dark Energy Constraints from Weak-Lensing Cross-Correlation Cosmography
We present a method for implementing the idea of Jain & Taylor for constraining cosmological parameters with weak gravitational lensing. Photometric redshift information on foreground galaxies is used to produce templates of the mass structure at foreground slices zl, and the predicted distortion field is cross-correlated with the measured shapes of sources at redshift zs. The variation of the cross-correlation
G. M. Bernstein; B. Jain
Gravitational lensing by clusters of galaxies - Constraining the mass distribution
NASA Technical Reports Server (NTRS)
The possibility of placing constraints on the mass distribution of a cluster of galaxies by analyzing the cluster's gravitational lensing effect on the images of more distant galaxies is investigated theoretically in the limit of weak distortion. The steps in the proposed analysis are examined in detail, and it is concluded that detectable distortion can be produced by clusters with line-of-sight velocity dispersions of over 500 km/sec. Hence it should be possible to determine (1) the cluster center position (with accuracy equal to the mean separation of the background galaxies), (2) the cluster-potential quadrupole moment (to within about 20 percent of the total potential if velocity dispersion is 1000 km/sec), and (3) the power law for the outer-cluster density profile (if enough background galaxies in the surrounding region are observed).
Miralda-Escude, Jordi
A dearth of dark matter in strong gravitational lenses
NASA Astrophysics Data System (ADS)
I show that the lensing masses of the Sloan Lens Advanced Camera Surveys sample of strong gravitational lenses are consistent with the stellar masses determined from population synthesis models using the Salpeter initial mass function. This is true in the context of both General Relativity and modified Newtonian dynamics (MOND), and is in agreement with the expectation of MOND that there should be little classical discrepancy within the high surface brightness regions probed by strong gravitational lensing. There is also dynamical evidence from this sample supporting the claim that the mass-to-light ratio of the stellar component increases with the velocity dispersion.
Sanders, R. H.
On the gravitational lensing of type Ia supernovae
NASA Astrophysics Data System (ADS)
Gravitational lensing has turned out to be an active field in astronomy, both as an abstract subject and a means to better understand and study other astronomical topics. One of the main applications of gravitational lensing is the broad field of supernovae observation. It is shown that lensing can have dramatic effects on how supernovae are observed, and therefore appear as an inevitable 'noise' in any (deep) survey carried out for purposes such as determining the equation of state for the so-called dark energy. In this dissertation we concentrate on some of these effects on the observation of type Ia supernovae.
Bagherpour, Hamed
The weak gravitational lensing of distant galaxies by a large-scale structure is expected to become a powerful probe of dark energy. By measuring the ellipticities of large number of background galaxies, the subtle gravitational distortion called 'cosmic shear' can be measured and used to constrain dark energy parameters. The observed galaxy ellipticities, however, are induced not by shear but by reduced shear, which also accounts for slight magnifications of the images. This distinction is negligible for present weak-lensing surveys, but it will become more important as we improve our ability to measure and understand small-angle cosmic shear modes. I calculate the discrepancy between shear and reduced shear in the context of power spectra and cross spectra, finding the difference could be as high as 10% on the smallest accessible angular scales. I estimate how this difference will bias dark energy parameters obtained from two weak-lensing methods: weak-lensing tomography and the shear ratio method known as offset-linear scaling. For weak-lensing tomography, ignoring the effects of reduced shear will cause future surveys considered by the Dark Energy Task Force to measure dark energy parameters that are biased by amounts comparable to their error bars. I advocate that reduced shear be properly accounted for in such surveys, and I provide a semi-analytic formula for doing so. Since reduced shear cross spectra do not follow an offset-linear scaling relation, the shear ratio method is similarly biased but with smaller significance.
Shapiro, Charles [Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 2EG (United Kingdom)], E-mail: email@example.com
Gravitational Lenses and the Structure and Evolution of Galaxies
NASA Technical Reports Server (NTRS)
The grant has supported the completion of 16 papers and 4 conference proceedings to date. During the first year of the project we completed five papers, each of which represents a new direction in the theory and interpretation of gravitational lenses. In the first paper, "The Importance of Einstein Rings", we developed the first theory for the formation and structure of the Einstein rings formed by lensing extended sources like the host galaxies of quasar and radio sources. We applied the theory to three lenses with lensed host galaxies. For the time delay lens PG 1115+080 we found that the structure of the Einstein ring ruled out models of the gravitational potential which permitted a large Hubble constant (70 km/s Mpc). In the second paper, :Cusped Mass Models Of Gravitational Lenses", we introduced a new class of lens models where the central density is characterized by a cusp ( rho proportional to tau(sup -gamma), 1 less than gamma less than 2) as in most modern models and theories of galaxies rather than a finite core radius. In the third paper, "Global Probes of the Impact of Baryons on Dark Matter Halos", we made the first globally consistent models for the separation distribution of gravitational lenses including both galaxy and cluster lenses. We show that the key physics for the origin of the sharp separation cutoff in the separation distribution near 3 arc sec is the effect of the cooling baryons in galaxies on the density structure of the system.
Kochanek, Christopher
Mapping cluster mass distributions via gravitational lensing of background galaxies
We present a new method for measuring the projected mass distributions of galaxy clusters, based solely on the gravitational lens amplification of background galaxies by the cluster potential field. The gravitational amplification is measured by comparing the joint distribution in redshift and magnitude of galaxies behind the cluster with that of the average distribution of field galaxies. Lensing shifts the
T. J. Broadhurst; A. N. Taylor; J. A. Peacock
Scaling the universe: Gravitational lenses and the Hubble constant
Gravitational lenses, besides being interesting in their own right, have been demonstrated to be suitable as �gravitational standard rulers� for the measurement of the rate of expansion of the Universe (Ho), as well as to constrain the values of the cosmological parameters such as ?o and ?o that control the evolution of the volume of the Universe with cosmic time.
Myers, Steven T.
Gravitational lensing in a non-uniform plasma
NASA Astrophysics Data System (ADS)
We develop a model of gravitational lensing in a non-uniform plasma. When a gravitating body is surrounded by a plasma, the lensing angle depends on the frequency of the electromagnetic wave, due to the dispersion properties of the plasma, in the presence of a plasma inhomogeneity, and of gravity. The second effect leads, even in a uniform plasma, to a difference of the gravitational photon deflection angle from the vacuum case, and to its dependence on the photon frequency. We take into account both effects, and derive the expression for the lensing angle in the case of a strongly non-uniform plasma in the presence of gravitation. The dependence of the lensing angle on the photon frequency in a homogeneous plasma resembles the properties of a refractive prism spectrometer, the strongest action of which is for very long radio waves. We discuss the observational appearance of this effect for the gravitational lens with a Schwarzschild metric, surrounded by a uniform plasma. We obtain formulae for the lensing angle and the magnification factors in this case and discuss the possibility of observation of this effect by the planned very long baseline interferometry space project RadioAstron. We also consider models with a non-uniform plasma distribution. For different gravitational lens models we compare the corrections to the vacuum lensing due to the gravitational effect in the plasma, and due to the plasma inhomogeneity. We show that the gravitational effect could be detected in the case of a hot gas in the gravitational field of a galaxy cluster.
Bisnovatyi-Kogan, G. S.; Tsupko, O. Yu.
Constraints on cosmological models from strong gravitational lensing systems
NASA Astrophysics Data System (ADS)
Strong lensing has developed into an important astrophysical tool for probing both cosmology and galaxies (their structure, formation, and evolution). Using the gravitational lensing theory and cluster mass distribution model, we try to collect a relatively complete observational data concerning the Hubble constant independent ratio between two angular diameter distances Dds/Ds from various large systematic gravitational lens surveys and lensing by galaxy clusters combined with X-ray observations, and check the possibility to use it in the future as complementary to other cosmological probes. On one hand, strongly gravitationally lensed quasar-galaxy systems create such a new opportunity by combining stellar kinematics (central velocity dispersion measurements) with lensing geometry (Einstein radius determination from position of images). We apply such a method to a combined gravitational lens data set including 70 data points from Sloan Lens ACS (SLACS) and Lens Structure and Dynamics survey (LSD). On the other hand, a new sample of 10 lensing galaxy clusters with redshifts ranging from 0.1 to 0.6 carefully selected from strong gravitational lensing systems with both X-ray satellite observations and optical giant luminous arcs, is also used to constrain three dark energy models (?CDM, constant w and CPL) under a flat universe assumption. For the full sample (n = 80) and the restricted sample (n = 46) including 36 two-image lenses and 10 strong lensing arcs, we obtain relatively good fitting values of basic cosmological parameters, which generally agree with the results already known in the literature. This results encourages further development of this method and its use on larger samples obtained in the future.
Cao, Shuo; Pan, Yu; Biesiada, Marek; Godlowski, Wlodzimierz; Zhu, Zong-Hong
Cosmological information in weak lensing peaks
NASA Astrophysics Data System (ADS)
Recent studies have shown that the number counts of convergence peaks N(?) in weak lensing (WL) maps, expected from large forthcoming surveys, can be a useful probe of cosmology. We follow up on this finding, and use a suite of WL convergence maps, obtained from ray-tracing N-body simulations, to study (i) the physical origin of WL peaks with different heights, and (ii) whether the peaks contain information beyond the convergence power spectrum P?. In agreement with earlier work, we find that high peaks (with amplitudes ?3.5?, where ? is the r.m.s. of the convergence ?) are typically dominated by a single massive halo. In contrast, medium-height peaks (?0.5-1.5?) cannot be attributed to a single collapsed dark matter halo, and are instead created by the projection of multiple (typically, 4-8) halos along the line of sight, and by random galaxy shape noise. Nevertheless, these peaks dominate the sensitivity to the cosmological parameters w, ?8, and ?m. We find that the peak-height distribution and its dependence on cosmology differ significantly from predictions in a Gaussian random field. We directly compute the marginalized errors on w, ?8, and ?m from the N(?)+P? combination, including redshift tomography with source galaxies at zs=1 and zs=2. We find that the N(?)+P? combination has approximately twice the cosmological sensitivity compared to P? alone. These results demonstrate that N(?) contains non-Gaussian information complementary to the power spectrum.
Yang, Xiuyuan; Kratochvil, Jan M.; Wang, Sheng; Lim, Eugene A.; Haiman, Zolt�n; May, Morgan
Flux-limited strong gravitational lensing and dark energy
NASA Astrophysics Data System (ADS)
In the standard flat cosmological constant (?) cold dark matter (CDM) cosmology, a model of two populations of lens halos for strong gravitational lensing can reproduce the results of the Jodrell-Bank VLA Astrometric Survey (JVAS) and the Cosmic Lens All-Sky Survey (CLASS) radio survey. In such a model, lensing probabilities are sensitive to three parameters: the concentration parameter c1, the cooling mass scale Mc and the value of the CDM power spectrum normalization parameter ?8. The value ranges of these parameters are constrained by various observations. However, we found that predicted lensing probabilities are also quite sensitive to the flux density (brightness) ratio qr of the multiple lensing images, which has been a very important selection criterion of a sample in any lensing survey experiments. We re-examine the mentioned above model by considering the flux ratio and galactic central Super Massive Black Holes (SMBHs), in flat, low-density cosmological models with different cosmic equations of state ?, and find that the predicted lensing probabilities without considering qr are over-estimated. A low value of qr can be compensated for by raising the cooling mass scale Mc in fitting the predicted lensing probabilities to JVAS/CLASS observations. To determine the cosmic equation of state ?, the uncertainty in Mc must be resolved. The effects of SMBHs cannot be detected by strong gravitational lensing methods when qr? 10.
Chen, D.-M.
Weak lensing of CMB by cosmic (super-)strings
We study the effect of weak lensing by cosmic (super-)strings on the anisotropies of cosmic microwave background (CMB). In developing a method to calculate the lensing convergence field due to strings, and thereby temperature and polarization angular power spectra of CMB, we clarify how the nature of strings, characterized by the intercommuting probability, can influence these CMB anisotropies. We find
Daisuke Yamauchi; Keitaro Takahashi; Yuuiti Sendouda; Chul-Moon Yoo
Gravitational Lenses and the Structure and Evolution of Galaxies
NASA Technical Reports Server (NTRS)
During the first year of the project we completed five papers, each of which represents a new direction in the theory and interpretation of gravitational lenses. In the first paper, The Importance of Einstein Rings, we developed the first theory for the formation and structure of the Einstein rings formed by lensing extended sources like the host galaxies of quasar and radio sources. In the second paper, Cusped Mass Models Of Gravitational Lenses, we introduced a new class of lens models. In the third paper, Global Probes of the Impact of Baryons on Dark Matter Halos, we made the first globally consistent models for the separation distribution of gravitational lenses including both galaxy and cluster lenses. The last two papers explore the properties of two lenses in detail. During the second year we have focused more closely on the relationship of baryons and dark matter. In the third year we have been further examining the relationship between baryons and dark matter. In the present year we extended our statistical analysis of lens mass distributions using a self-similar model for the halo mass distribution as compared to the luminous galaxy.
Oliversen, Ronald J. (Technical Monitor); Kochanek, Christopher
GREAT3: The Third Gravitational Lensing Accuracy Testing Challenge
NASA Astrophysics Data System (ADS)
We describe the upcoming weak lensing community data challenge, GREAT3, and the associated open-source image simulation software, GalSim. The GREAT3 challenge will test the impact on weak lensing measurements of (a) realistic galaxy morphologies, (b) realistic uncertainty in the point-spread function estimation, and (c) the need to combine multiple exposures when estimating the galaxy shape. It will include simulated ground- and space-based data, and the tests of realistic galaxy morphologies will rely on a training set of galaxies from the Hubble Space Telescope which will be publicly released at the start of the challenge. We describe some technical considerations for generating the challenge data and for testing weak lensing measurements with the next generation of weak lensing surveys, such as DES, HSC, KIDS, and Pan-STARRS.
Mandelbaum, Rachel; Rowe, B.; GREAT3 Collaboration
Gravitational lensing shear by an exotic lens object with negative convergence or negative mass
NASA Astrophysics Data System (ADS)
Gravitational lens models with negative convergence (surface mass density projected onto the lens plane) inspired by modified gravity theories, exotic matter, and energy have been recently discussed in such a way that a static and spherically symmetric modified spacetime metric depends on the inverse distance to the power of positive n (n=1 for Schwarzschild metric, n=2 for Ellis wormhole) in the weak-field approximation [T. Kitamura, K. Nakajima, and H. Asada, Phys. Rev. D 87, 027501 (2013)], and it has been shown that demagnification of images could occur for n>1 lens models associated with exotic matter (and energy), though they cause the gravitational pull on light rays. The present paper considers gravitational lensing shear by the demagnifying lens models and other models such as negative-mass compact objects causing the gravitational repulsion on light rays like a concave lens. It is shown that images by the lens models for the gravitational pull are tangentially elongated, whereas those by the repulsive ones are radially distorted. This feature of lensed image shapes may be used for searching (or constraining) localized exotic matter or energy with gravitational lensing surveys. It is suggested also that an underdense region such as a cosmic void might produce radially elongated images of background galaxies rather than tangential ones.
Izumi, Koji; Hagiwara, Chisaki; Nakajima, Koki; Kitamura, Takao; Asada, Hideki
The impact of camera optical alignments on weak lensing measures for the Dark Energy Survey
NASA Astrophysics Data System (ADS)
Telescope point spread function (PSF) quality is critical for realizing the potential of cosmic weak lensing observations to constrain dark energy and test general relativity. In this paper, we use quantitative weak gravitational lensing measures to inform the precision of lens optical alignment, with specific reference to the Dark Energy Survey (DES). We compute optics spot diagrams and calculate the shear and flexion of the PSF as a function of position on the focal plane. For perfect optical alignment, we verify the high quality of the DES optical design, finding a maximum PSF contribution to the weak lensing shear of 0.04 near the edge of the focal plane. However, this can be increased by a factor of approximately 3 if the lenses are only just aligned within their maximum specified tolerances. We calculate the E- and B-mode shear and flexion variance as a function of the decentre or tilt of each lens in turn. We find tilt accuracy to be a few times more important than decentre, depending on the lens considered. Finally, we consider the compound effect of decentre and tilt of multiple lenses simultaneously, by sampling from a plausible range of values of each parameter. We find that the compound effect can be around twice as detrimental as when considering any one lens alone. Furthermore, this combined effect changes the conclusions about which lens is most important to align accurately. For DES, the tilt of the first two lenses is the most important.
Antonik, Michelle L.; Bacon, David J.; Bridle, Sarah; Doel, Peter; Brooks, David; Worswick, Sue; Bernstein, Gary; Bernstein, Rebecca; DePoy, Darren; Flaugher, Brenna; Frieman, Joshua A.; Gladders, Michael; Gutierrez, Gaston; Jain, Bhuvnesh; Jarvis, Michael; Kent, Stephen M.; Lahav, Ofer; Parker, S.-J.; Roodman, Aaron; Walker, Alistair R.
Herschel HerMES: Gravitationally Lensed Galaxies and Lensing Statistics at Submillimeter Wavelengths
NASA Astrophysics Data System (ADS)
Strong gravitational lensing provides a boost in the apparent flux and angular size of distant galaxies, enabling the study of high-redshift populations in unprecedented detail. Furthermore, the lensing distortion also establishes a measure of the total mass of the foreground deflector, and is therefore useful to study the distribution of dark matter in foreground structures. Using Herschel HerMES data we have compiled the largest catalog to date ( 90 sources) of distant submillimeter galaxies (SMGs) that are candidates for being strongly gravitationally lensed by individual foreground galaxies. Candidate identification is straightforward due to the steep bright-end slope of the intrinsic SMG number counts -- we simply select sources that are brighter than 80mJy at 500?m and remove local (z< 0.1) spiral galaxies and radio-loud AGN. The candidate lensed galaxies have submillimeter colors that are consistent with high-redshift galaxies and that are typical of Herschel-selected sources. A simple model of the lensing rate, based on the intrinsic SMG number counts and a foreground dark matter distribution, predicts that our candidates have high fidelity, with 40--90% of them lensed by a factor of ?2. The model also predicts that the average magnification of the lensed SMGs increases with apparent 500?m flux and is a factor of 2--10 for the sources in our sample (S500=80--200mJy). Follow-up programs to target the candidate lensed galaxies are ongoing and initial results confirm the lensing nature of several systems. The typical SMG in these systems lies at z 3 and is lensed by a galaxy at z 0.5. The observed lensing magnifications are factors of 3--20, with the majority of observed sources magnified by factors < 10.
Wardlow, Julie L.; Cooray, A.; De Bernardis, F.; HerMES Collaboration
Strong gravitational lensing with Gauss-Bonnet correction
NASA Astrophysics Data System (ADS)
In this paper we investigate the strong gravitational lensing in a five dimensional background with Gauss-Bonnet gravity, so that in 4-dimensions the Gauss-Bonnet correction disappears. By considering the logarithmic term for deflection angle, we obtain the deflection angle hat alpha and corresponding parameters ? and bar b. Finally, we estimate some properties of relativistic images such as ??, s and rm.
Sadeghi, J.; Vaez, H.
CFHTLenS tomographic weak lensing: quantifying accurate redshift distributions
NASA Astrophysics Data System (ADS)
The Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) comprises deep multicolour (u*g'r'i'z') photometry spanning 154 deg2, with accurate photometric redshifts and shape measurements. We demonstrate that the redshift probability distribution function summed over galaxies provides an accurate representation of the galaxy redshift distribution accounting for random and catastrophic errors for galaxies with best-fitting photometric redshifts zp < 1.3. We present cosmological constraints using tomographic weak gravitational lensing by large-scale structure. We use two broad redshift bins 0.5 < zp ? 0.85 and 0.85 < zp ? 1.3 free of intrinsic alignment contamination, and measure the shear correlation function on angular scales in the range �1-40 arcmin. We show that the problematic redshift scaling of the shear signal, found in previous Canada-France-Hawaii Telescope Legacy Survey data analyses, does not affect the CFHTLenS data. For a flat ? cold dark matter model and a fixed matter density ?m = 0.27, we find the normalization of the matter power spectrum ?8 = 0.771 � 0.041. When combined with cosmic microwave background data (Wilkinson Microwave Anisotropy Probe 7-year results), baryon acoustic oscillation data (BOSS) and a prior on the Hubble constant from the Hubble Space Telescope distance ladder, we find that CFHTLenS improves the precision of the fully marginalized parameter estimates by an average factor of 1.5-2. Combining our results with the above cosmological probes, we find ?m = 0.2762 � 0.0074 and ?8 = 0.802 � 0.013.
Benjamin, Jonathan; Van Waerbeke, Ludovic; Heymans, Catherine; Kilbinger, Martin; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Kitching, Thomas D.; Mellier, Yannick; Miller, Lance; Rowe, Barnaby; Schrabback, Tim; Simpson, Fergus; Coupon, Jean; Fu, Liping; Harnois-D�raps, Joachim; Hudson, Michael J.; Kuijken, Konrad; Semboloni, Elisabetta; Vafaei, Sanaz; Velander, Malin
Reverberation Mapping of a Gravitationally-lensed Quasar
NASA Astrophysics Data System (ADS)
We propose a continuation of the program we began in 2013B to perform reverberation mapping on a gravitationally lensed quasar. Gravitationally lensed quasars are already rich test beds for studying cosmology, black hole accretion physics, dark matter, and galaxy properties. Here, we will expand their use by spectroscopically monitoring the CIV quasar emission line with GMOS to measure the broad line region size and black hole mass of the z=1.7 lensed quasar HE0435-1223. The success of this program has significant implications for studies of quasar physics, galaxy evolution at high redshift, and further studies of cosmology, and it is possible with only a modest addition (<2.5 nights) of Gemini time in 2014A.
Denney, Kelly D.; Courbin, Frederic; Kochanek, Christopher S.; MacLeod, Chelsea L.; Meylan, Georges; Morgan, Christopher W.; Mosquera, Ana; Moustakas, Leonidas; Onken, Christopher A.; Peterson, Bradley M.; Sluse, Dominique
Strong lensing of gravitational waves as seen by LISA.
We discuss strong gravitational lensing of gravitational waves from the merging of massive black hole binaries in the context of the LISA mission. Detection of multiple events would provide invaluable information on competing theories of gravity, evolution and formation of structures and, possibly, constraints on H0 and other cosmological parameters. Most of the optical depth for lensing is provided by intervening massive galactic halos, for which wave optics effects are negligible. Probabilities to observe multiple events are sizable for a broad range of formation histories. For the most optimistic models, up to ? 4 multiple events with a signal to noise ratio ? 8 are expected in a 5-year mission. Chances are significant even for conservative models with either light (? 60%) or heavy (? 40%) seeds. Because of lensing amplification, some intrinsically too faint signals are brought over threshold (? 2 per year). PMID:21231571
Sereno, M; Sesana, A; Bleuler, A; Jetzer, Ph; Volonteri, M; Begelman, M C
Quasar 4C71.07: a gravitationally lensed quasar revealed by polarization VLBI?
NASA Astrophysics Data System (ADS)
The effects of weak gravitational lensing by a galaxy lens model are shown to provide a possible explanation for the observed misalignment of 28��4� between the magnetic field and jet position angles in the quasar 4C71.07. Preliminary results indicate that a lens of mass ?1011Msun at a redshift of z = 0.9 would lie ?0.25 arcseconds from the image.
Hutchison, J. M.; Cawthorne, T. V.
Topics in gravitational lensing: Clusters, quasars, and the cosmic microwave background
NASA Astrophysics Data System (ADS)
Several different cosmological applications of gravitational lensing, both weak and strong, are addressed from both a theoretical and observational perspective. First, we study the potential of weak lensing surveys to detect clusters of galaxies, using a fast Particle Mesh cosmological N-body simulation algorithm specifically tailored to investigate the statistics of these shear- selected clusters. We then consider how weak lensing might be used as a tool to isolate secondary anisotropies of the cosmic microwave background (CMB) through cross-correlation. It is shown that a cross-correlation of the small angular scale CMB with an overlapping weak-lensing survey should be detectable with high signal to noise ratio, and will isolate the elusive kinetic Sunyaev-Zel ' dovich (kSZ) effect from secondary anisotropies generated at higher redshifts. Next we discuss strong gravitational lensing, and study the expected properties and statistics of giant arcs and multiply imaged quasars, produced by galaxy clusters in a cold dark matter (CDM) universe with a cosmological constant (ACDM). This is done by carrying out a large ensemble of ray tracing simulations through clusters from a cosmological N-body simulation of the ACDM cosmology. Our results are compared to current surveys for giant arcs and multiply imaged quasars. Our large ensemble of simulations also allows us to statistically characterize the cluster lens population, and we explore how the properties of cluster lenses differ from the total population of galaxy clusters. Finally, the results of an observational effort to discover close pairs of quasars are presented. The goal of this quasar pair survey is to find quasars multiply imaged by clusters and to find binary quasars which can be used to study quasar clustering on small scales. A sample of 59 new quasar pairs discovered in this program which we use to demonstrate that quasars exhibit excess clustering on small scales 20 h -1 kpc-1 h -1 Mpc.
Hennawi, Joseph F.
Strong gravitational lensing in a noncommutative black-hole spacetime
Noncommutative geometry may be a starting point to a quantum gravity. We study the influence of the spacetime noncommutative parameter on the strong field gravitational lensing in the noncommutative Schwarzschild black-hole spacetime and obtain the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy can be described by this metric, we estimate the numerical values of the coefficients and observables for strong gravitational lensing. In comparison to the Reissner-Norstroem black hole, we find that the influences of the spacetime noncommutative parameter is similar to those of the charge, but these influences are much smaller. This may offer a way to distinguish a noncommutative black hole from a Reissner-Norstroem black hole, and may permit us to probe the spacetime noncommutative constant {theta} by the astronomical instruments in the future.
Ding Chikun; Kang Shuai; Chen Changyong; Chen Songbai; Jing Jiliang [Department of Physics and Information Engineering, Hunan Institute of Humanities Science and Technology, Loudi, Hunan 417000 (China); Institute of Physics and Department of Physics, Hunan Normal University, Changsha, Hunan 410081 (China) and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control (Hunan Normal University), Ministry of Education (China)
Evidence of the accelerated expansion of the Universe from weak lensing tomography with COSMOS
NASA Astrophysics Data System (ADS)
We present a comprehensive analysis of weak gravitational lensing by large-scale structure in the Hubble Space Telescope Cosmic Evolution Survey (COSMOS), in which we combine space-based galaxy shape measurements with ground-based photometric redshifts to study the redshift dependence of the lensing signal and constrain cosmological parameters. After applying our weak lensing-optimized data reduction, principal-component interpolation for the spatially, and temporally varying ACS point-spread function, and improved modelling of charge-transfer inefficiency, we measured a lensing signal that is consistent with pure gravitational modes and no significant shape systematics. We carefully estimated the statistical uncertainty from simulated COSMOS-like fields obtained from ray-tracing through the Millennium Simulation, including the full non-Gaussian sampling variance. We tested our lensing pipeline on simulated space-based data, recalibrated non-linear power spectrum corrections using the ray-tracing analysis, employed photometric redshift information to reduce potential contamination by intrinsic galaxy alignments, and marginalized over systematic uncertainties. We find that the weak lensing signal scales with redshift as expected from general relativity for a concordance ?CDM cosmology, including the full cross-correlations between different redshift bins. Assuming a flat ?CDM cosmology, we measure ?_8(?_m/0.3)0.51 = 0.75�0.08 from lensing, in perfect agreement with WMAP-5, yielding joint constraints ?_m = 0.266+0.025-0.023, ?_8 = 0.802+0.028-0.029 (all 68.3% conf.). Dropping the assumption of flatness and using priors from the HST Key Project and Big-Bang nucleosynthesis only, we find a negative deceleration parameter q0 at 94.3% confidence from the tomographic lensing analysis, providing independent evidence of the accelerated expansion of the Universe. For a flat wCDM cosmology and prior w ? [-2,0], we obtain w <-0.41 (90% conf.). Our dark energy constraints are still relatively weak solely due to the limited area of COSMOS. However, they provide an important demonstration of the usefulness of tomographic weak lensing measurements from space. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archives at the Space Telescope European Coordinating Facility and the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.
Schrabback, T.; Hartlap, J.; Joachimi, B.; Kilbinger, M.; Simon, P.; Benabed, K.; Brada?, M.; Eifler, T.; Erben, T.; Fassnacht, C. D.; High, F. William; Hilbert, S.; Hildebrandt, H.; Hoekstra, H.; Kuijken, K.; Marshall, P. J.; Mellier, Y.; Morganson, E.; Schneider, P.; Semboloni, E.; van Waerbeke, L.; Velander, M.
Gravitational lenses: The current sample, recent results, and continuing searches
NASA Technical Reports Server (NTRS)
Gravitational lensing is one of the topics in astrophysics that was quite extensively discussed over time before it was actually discovered. Ten years after the discovery of the first one, it is interesting to note how the field has developed. After an initial slow rate of discovery, the last few years have seen an explosion in the number of reported cases. Attention was drawn to the first few cases because quasars at the same red shift, with similar optical spectra, were observed with angular separations of only a few arc seconds. Most observational effort has been devoted to searching for new candidate lens systems and carefully measuring their properties, both to test whether they are indeed lensed and to provide constraints for modeling. A classification of the lenses is into rings, arcs, multiples, and doubles, where the progression is from sources close to the optical axis to far from the optical axis. The known candidate systems are listed. The searches for gravitational lenses are proving to be successful, and more lenses continue to be discovered serendipitously. Many searches are under way, along with instruments that will routinely increase the resolution of astronomical imaging.
Hewitt, Jacqueline N.
Gravitational Lensing by Clusters of Galaxies
NASA Astrophysics Data System (ADS)
CLUSTERS OF GALAXIES are massive and relatively rare objects containing hundreds of galaxies. Their huge mass�dominated by DARK MATTER�bends light from all background objects, systematically distorting the images of thousands of distant galaxies (shear). This observed gravitational lens distortion can be inverted to produce an `image' of the mass in the foreground cluster of galaxies. Most of the...
Tyson, J.; Murdin, P.
General requirements on matter power spectrum predictions for cosmology with weak lensing tomography
NASA Astrophysics Data System (ADS)
Forthcoming projects such as DES, LSST, WFIRST, and Euclid aim to measure weak lensing shear correlations with unprecedented precision, constraining the dark energy equation of state at the percent level. Reliance on photometrically-determined redshifts constitutes a major source of uncertainty for these surveys. Additionally, interpreting the weak lensing signal requires a detailed understanding of the nonlinear physics of gravitational collapse. We present a new analysis of the stringent calibration requirements for weak lensing analyses of future imaging surveys that addresses both photo-z uncertainty and errors in the calibration of the matter power spectrum. We find that when photo-z uncertainty is taken into account the requirements on the level of precision in the prediction for the matter power spectrum are more stringent than previously thought. Including degree-scale galaxy clustering statistics in a joint analysis with weak lensing not only strengthens the survey's constraining power by ~ 20%, but can also have a profound impact on the calibration demands, decreasing the degradation in dark energy constraints with matter power spectrum uncertainty by a factor of 2-5. Similarly, using galaxy clustering information significantly relaxes the demands on photo-z calibration. We compare these calibration requirements to the contemporary state-of-the-art in photometric redshift estimation and predictions of the power spectrum and suggest strategies to utilize forthcoming data optimally.
Hearin, Andrew P.; Zentner, Andrew R.; Ma, Zhaoming
Lensing Effects on Gravitational Waves in a Clumpy Universe
NASA Astrophysics Data System (ADS)
The distance-redshift relation via gravitational waves in the clumpy universe is simulated numerically by taking account of the effects of gravitational lensing. It is assumed that all of the matter in the universe takes the form of randomly distributed point masses, each of which has the identical mass ML. Calculations are carried out in the two extreme cases: ? ? GML/c2 and ? ? GML/c2, where ? denotes the wavelength of gravitational waves. In the former, the distance-redshift relation for the fully homogeneous and isotropic universe is reproduced with small distance dispersion, whereas, in the latter, the distance dispersion is larger. This result suggests that we might obtain the information about the typical mass of lens objects through the distance-redshift relation gleaned through observation of gravitational waves of various wavelengths.
Yoo, Chul-Moon; Nakao, Ken-Ichi; Kozaki, Hiroshi; Takahashi, Ryuichi
The Effect of Weak Lensing on Distance Estimates from Supernovae
NASA Astrophysics Data System (ADS)
Using a sample of 608 Type Ia supernovae from the SDSS-II and BOSS surveys, combined with a sample of foreground galaxies from SDSS-II, we estimate the weak lensing convergence for each supernova line of sight. We find that the correlation between this measurement and the Hubble residuals is consistent with the prediction from lensing (at a significance of 1.7?). Strong correlations are also found between the residuals and supernova nuisance parameters after a linear correction is applied. When these other correlations are taken into account, the lensing signal is detected at 1.4?. We show, for the first time, that distance estimates from supernovae can be improved when lensing is incorporated, by including a new parameter in the SALT2 methodology for determining distance moduli. The recovered value of the new parameter is consistent with the lensing prediction. Using cosmic microwave background data from WMAP7, H 0 data from Hubble Space Telescope and Sloan Digital Sky Survey (SDSS) Baryon acoustic oscillations measurements, we find the best-fit value of the new lensing parameter and show that the central values and uncertainties on ? m and w are unaffected. The lensing of supernovae, while only seen at marginal significance in this low-redshift sample, will be of vital importance for the next generation of surveys, such as DES and LSST, which will be systematics-dominated.
Smith, Mathew; Bacon, David J.; Nichol, Robert C.; Campbell, Heather; Clarkson, Chris; Maartens, Roy; D'Andrea, Chris B.; Bassett, Bruce A.; Cinabro, David; Finley, David A.; Frieman, Joshua A.; Galbany, Lluis; Garnavich, Peter M.; Olmstead, Matthew D.; Schneider, Donald P.; Shapiro, Charles; Sollerman, Jesper
Scatter and bias in weak lensing selected clusters
NASA Astrophysics Data System (ADS)
We examine scatter and bias in weak lensing selected clusters, employing both an analytic model of dark matter haloes and numerical mock data of weak lensing cluster surveys. We pay special attention to effects of the diversity of dark matter distributions within clusters. We find that peak heights of the lensing convergence map correlate rather poorly with the virial mass of haloes. The correlation is tighter for the spherical overdensity mass with a higher mean interior density (e.g. M1000). We examine the dependence of the halo shape on the peak heights, and find that the root mean square scatter caused by the halo diversity scales linearly with the peak heights with the proportionality factor of 0.1-0.2. The noise originated from the halo shape is found to be comparable to the source galaxy shape noise and the cosmic shear noise. We find the significant halo orientation bias, i.e. weak lensing selected clusters on average have their major axes aligned with the line-of-sight direction, and that the orientation bias is stronger for higher signal-to-noise ratio (S/N) peaks. We compute the orientation bias using an analytic triaxial halo model and obtain results quite consistent with the ray-tracing results. We develop a prescription to analytically compute the number count of weak lensing peaks taking into account all the main sources of scatters in the peak heights. We find that the improved analytic predictions agree well with the simulation results for high-S/N peaks of ??5. We also compare the expected number count with our weak lensing analysis results for 4 deg2 of Subaru/Suprime-Cam observations and find a good agreement.
Hamana, Takashi; Oguri, Masamune; Shirasaki, Masato; Sato, Masanori
A Conceptual and Cultural History of Gravitational Lensing
NASA Astrophysics Data System (ADS)
By analysing the early ideas on the bending of light due to a gravitational attraction, which led to the concept of gravitational lenses, we attempt to present an undistorted historical and cultural perspective of the subject. We show that, contrary to a widespread belief, Newton did not ponder on this topic, and that the earliest thoughts possibly come from Marat and Cavendish. We briefly review the contributions by Soldner, Chwolson and Einstein and focus on the r�le of F. Link, who was undoubtedly the pioneer of the subject.
Valls-Gabaud, D.
Wave effect in gravitational lensing by the Ellis wormhole
NASA Astrophysics Data System (ADS)
We propose the use of modulated spectra of astronomical sources due to gravitational lensing to probe Ellis wormholes. The modulation factor due to gravitational lensing by the Ellis wormhole is calculated. Within the geometrical optics approximation, the normal point-mass lens and the Ellis wormhole are indistinguishable unless we know the source�s unlensed luminosity. This degeneracy is resolved with the significant wave effect in the low-frequency domain if we take the deviation from the geometrical optics into account. We can roughly estimate the upper bound for the number density of Ellis wormholes as n?4�10-10AU-3 with throat radius a�1cm from the existing femtolensing analysis for compact objects.
Yoo, Chul-Moon; Harada, Tomohiro; Tsukamoto, Naoki
Gravitational Lensing Constraint on the Cosmic Equation of State
NASA Astrophysics Data System (ADS)
Recent redshift-distance measurements of Type Ia supernovae (SNe Ia) at cosmological distances suggest that two-third of the energy density of the universe is dominated by dark energy component with an effective negative pressure. This dark energy component is described by the equation of state px = w?x (w ? - 1). We use gravitational lensing statistics to constrain the equation of state of this dark energy. We use n(??), the image separation distribution function of lensed quasars, as a tool to probe w. We find that for the observed range of ?m ~ 0.2 0.4, w should lie between -0.8 ? w ? -0.4 in order to have five lensed quasars in a sample of 867 optical quasars. This limit is highly sensitive to lens and Schechter parameters and the evolution of galaxies.
Jain, Deepak; Dev, Abha; Panchapakesan, N.; Mahajan, S.; Bhatia, V. B.
Time delays for eleven gravitationally lensed quasars revisited
NASA Astrophysics Data System (ADS)
Aims: We test the robustness of published time delays for 11 lensed quasars by using two techniques to measure time shifts in their light curves. Methods: We chose to use two fundamentally different techniques to determine time delays in gravitationally lensed quasars: a method based on fitting a numerical model and another one derived from the minimum dispersion method introduced by Pelt and collaborators. To analyse our sample in a homogeneous way and avoid bias caused by the choice of the method used, we apply both methods to 11 different lensed systems for which delays have been published: JVAS B0218+357, SBS 0909+523, RX J0911+0551, FBQS J0951+2635, HE 1104-1805, PG 1115+080, JVAS B1422+231, SBS 1520+530, CLASS B1600+434, CLASS B1608+656, and HE 2149-2745 Results: Time delays for three double lenses, JVAS B0218+357, HE 1104-1805, and CLASS B1600+434, as well as the quadruply lensed quasar CLASS B1608+656 are confirmed within the error bars. We correct the delay for SBS 1520+530. For PG 1115+080 and RX J0911+0551, the existence of a second solution on top of the published delay is revealed. The time delays in four systems, SBS 0909+523, FBQS J0951+2635, JVAS B1422+231, and HE 2149-2745 prove to be less reliable than previously claimed. Conclusions: If we wish to derive an estimate of H0 based on time delays in gravitationally lensed quasars, we need to obtain more robust light curves for most of these systems in order to achieve a higher accuracy and robustness on the time delays.
Eulaers, E.; Magain, P.
Strong gravitational lensing: Why no central black holes?
NASA Astrophysics Data System (ADS)
We investigate how central black holes (BHs) in galactic dark halos could affect strong gravitational lensing. The distribution of integral lensing probability with image separations are calculated for quasars of redshift 1.5 by foreground dark matter halos. The mass density of dark halos is taken to be the Navarro-Frenk-White (NFW) profile such that, when the mass of a halo is less than 1014 Msun, its central black holes or a bulge is included as a point mass. The relationship between the masses M of supermassive black holes and the total gravitational mass MDM of their host galaxy is adopted from the most recent literature. Only a flat Lambda CDM model is considered here. It is shown that, while a single black hole for each galaxy contributes considerable but not sufficient lensing probabilities at small image separations compared with those without black holes, the bulges (which are about 100-1000 times larger in mass than a typical black hole) would definitely contribute enough probability at small image separations, although it gives too high probabilities at large separation angles compared with lensing observations.
Chen, Da-Ming
Gravitational Lensing Bound on the Average Redshift of Gamma Ray Bursts in Models with Evolving Lenses
NASA Astrophysics Data System (ADS)
Identification of gravitationally lensed Gamma Ray Bursts (GRBs) in the BATSE 4B catalog can be used to constrain the average redshift
Jain, Deepak; Panchapakesan, N.; Mahajan, S.; Bhatia, V. B.
Galaxy cluster center detection methods with weak lensing
NASA Astrophysics Data System (ADS)
The precise location of galaxy cluster centers is a persistent problem in weak lensing mass estimates and in interpretations of clusters in a cosmological context. In this work, we test methods of centroid determination from weak lensing data and examine the effects of such self-calibration on the measured masses. Drawing on lensing data from the Sloan Digital Sky Survey Stripe 82, a 275 square degree region of coadded data in the Southern Galactic Cap, together with a catalog of MaxBCG clusters, we show that halo substructure as well as shape noise and stochasticity in galaxy positions limit the precision of such a self-calibration (in the context of Stripe 82, to � 500 h-1 kpc or larger) and bias the mass estimates around these points to a level that is likely unacceptable for the purposes of making cosmological measurements. We also project the usefulness of this technique in future surveys.
Simet, Melanie
A compressed sensing approach to 3D weak lensing
NASA Astrophysics Data System (ADS)
Context. Weak gravitational lensing is an ideal probe of the dark universe. In recent years, several linear methods have been developed to reconstruct the density distribution in the Universe in three dimensions, making use of photometric redshift information to determine the radial distribution of lensed sources. Aims: We aim to address three key problems seen in these methods; namely, the bias in the redshifts of detected objects, the line-of-sight smearing seen in reconstructions, and the damping of the amplitude of the reconstruction relative to the underlying density. We also aim to detect structures at higher redshifts than have previously been achieved, and to improve the line-of-sight resolution of our reconstructions. Methods: We considered the problem under the framework of compressed sensing (CS). Under the assumption that the data are sparse or compressible in an appropriate dictionary, we constructed a robust estimator and employ state-of-the-art convex optimisation methods to reconstruct the density contrast. For simplicity in implementation, and as a proof of concept of our method, we reduced the problem to one dimension, considering the reconstruction along each line of sight independently. We also assumed an idealised survey in which the redshifts of sources are known. Results: Despite the loss of information inherent in our one-dimensional implementation, we demonstrate that our method is able to accurately reproduce cluster haloes up to a redshift of zcl = 1.0, deeper than state-of-the-art linear methods. We directly compare our method with these linear methods, and demonstrate minimal radial smearing and redshift bias in our reconstructions, as well as a reduced damping of the reconstruction amplitude as compared to the linear methods. In addition, the CS framework allows us to consider an underdetermined inverse problem, thereby allowing us to reconstruct the density contrast at finer resolution than the input data. Conclusions: The CS approach allows us to recover the density distribution more accurately than current state-of-the-art linear methods. Specifically, it addresses three key problem areas inherent in linear methods. Moreover, we are able to achieve super-resolution and increased high-redshift sensitivity in our reconstructions.
Leonard, A.; Dup�, F.-X.; Starck, J.-L.
The HST Frontier Fields: Gravitational Lensing Models Release
NASA Astrophysics Data System (ADS)
The Hubble Frontier Fields (HFF) is a Director's Discretionary Time (DDT) program to deeply observe up to six massive strong-lensing galaxy clusters and six "blank" fields in parallel. These complementary observations will yield magnified and direct images of some of the most distant galaxies yet observed. The strongly lensed images will be our deepest views of our universe to date. Interpretation of some (but not all) observed properties of the strongly lensed galaxies requires gravitational lens modeling. In order to maximize the value of this public dataset to the extragalactic community, STScI commissioned five teams funded by NASA to derive the best possible lens models from existing data. After coordinating to share observational constraints, including measured redshifts of strongly lensed galaxies, the teams independently derived lens models using robust, established methodologies. STScI released these models to the community in October before HFF observations of the first cluster, Abell 2744. Here we describe these models as well as a web tool which allows users to extract magnification estimates with uncertainties from all models for any galaxy strongly lensed by a HFF cluster. Inputs are the galaxy's coordinates (RA and Dec), redshift, and (optionally) observed radius. We also discuss ongoing work to study lens model uncertainties by modeling simulated clusters.
Coe, Dan A.; Lotz, J.; Natarajan, P.; Richard, J.; Zitrin, A.; Kneib, J.; Ebeling, H.; Sharon, K.; Johnson, T.; Limousin, M.; Bradac, M.; Hoag, A.; Cain, B.; Merten, J.; Williams, L. L.; Sebesta, K.; Meneghetti, M.; Koekemoer, A. M.; Barker, E. A.
Reducing Systematic Error in Weak Lensing Cluster Surveys
NASA Astrophysics Data System (ADS)
Weak lensing provides an important route toward collecting samples of clusters of galaxies selected by mass. Subtle systematic errors in image reduction can compromise the power of this technique. We use the B-mode signal to quantify this systematic error and to test methods for reducing this error. We show that two procedures are efficient in suppressing systematic error in the B-mode: (1) refinement of the mosaic CCD warping procedure to conform to absolute celestial coordinates and (2) truncation of the smoothing procedure on a scale of 10'. Application of these procedures reduces the systematic error to 20% of its original amplitude. We provide an analytic expression for the distribution of the highest peaks in noise maps that can be used to estimate the fraction of false peaks in the weak-lensing ?-signal-to-noise ratio (S/N) maps as a function of the detection threshold. Based on this analysis, we select a threshold S/N = 4.56 for identifying an uncontaminated set of weak-lensing peaks in two test fields covering a total area of ~3 deg2. Taken together these fields contain seven peaks above the threshold. Among these, six are probable systems of galaxies and one is a superposition. We confirm the reliability of these peaks with dense redshift surveys, X-ray, and imaging observations. The systematic error reduction procedures we apply are general and can be applied to future large-area weak-lensing surveys. Our high-peak analysis suggests that with an S/N threshold of 4.5, there should be only 2.7 spurious weak-lensing peaks even in an area of 1000 deg2, where we expect ~2000 peaks based on our Subaru fields. Based in part on data collected at Subaru Telescope and obtained from the SMOKA, which is operated by the Astronomy Data Center, National Astronomical Observatory of Japan.
Utsumi, Yousuke; Miyazaki, Satoshi; Geller, Margaret J.; Dell'Antonio, Ian P.; Oguri, Masamune; Kurtz, Michael J.; Hamana, Takashi; Fabricant, Daniel G.
Weak lensing tomography with orthogonal polynomials
NASA Astrophysics Data System (ADS)
The topic of this paper is weak cosmic shear tomography where the line-of-sight weighting is carried out with a set of specifically constructed orthogonal polynomials, dubbed Tomography with Orthogonal Radial Distance Polynomial Systems (TaRDiS). We investigate the properties of these polynomials and employ weak convergence spectra, which have been obtained by weighting with these polynomials, for the estimation of cosmological parameters. We quantify their power in constraining parameters in a Fisher matrix technique and demonstrate how each polynomial projects out statistically independent information, and how the combination of multiple polynomials lifts degeneracies. The assumption of a reference cosmology is needed for the construction of the polynomials, and as a last point we investigate how errors in the construction with a wrong cosmological model propagate to misestimates in cosmological parameters. TaRDiS performs on a similar level as traditional tomographic methods and some key features of tomography are made easier to understand.
Sch�fer, Bj�rn Malte; Heisenberg, Lavinia
Testing the Dark Energy with Gravitational Lensing Statistics
NASA Astrophysics Data System (ADS)
We study the redshift distribution of two samples of early-type gravitational lenses, extracted from a larger collection of 122 systems, to constrain the cosmological constant in the ?CDM model and the parameters of a set of alternative dark energy models (XCDM, Dvali-Gabadadze-Porrati, and Ricci dark energy models), in a spatially flat universe. The likelihood is maximized for ?? = 0.70 � 0.09 when considering the sample excluding the Sloan Lens ACS systems (known to be biased toward large image-separation lenses) and no-evolution, and ?? = 0.81 � 0.05 when limiting to gravitational lenses with image separation ?? > 2'' and no-evolution. In both cases, results accounting for galaxy evolution are consistent within 1?. The present test supports the accelerated expansion, by excluding the null hypothesis (i.e., ?? = 0) at more than 4?, regardless of the chosen sample and assumptions on the galaxy evolution. A comparison between competitive world models is performed by means of the Bayesian information criterion. This shows that the simplest cosmological constant model�that has only one free parameter�is still preferred by the available data on the redshift distribution of gravitational lenses. We perform an analysis of the possible systematic effects, finding that the systematic errors due to sample incompleteness, galaxy evolution, and model uncertainties approximately equal the statistical errors, with present-day data. We find that the largest sources of systemic errors are the dynamical normalization and the high-velocity cutoff factor, followed by the faint-end slope of the velocity dispersion function.
Cao, Shuo; Covone, Giovanni; Zhu, Zong-Hong
Statistical and Systematic Errors in the Measurement of Weak-Lensing Minkowski Functionals: Application to the Canada-France-Hawaii Lensing Survey
NASA Astrophysics Data System (ADS)
The measurement of cosmic shear using weak gravitational lensing is a challenging task that involves a number of complicated procedures. We study in detail the systematic errors in the measurement of weak-lensing Minkowski Functionals (MFs). Specifically, we focus on systematics associated with galaxy shape measurements, photometric redshift errors, and shear calibration correction. We first generate mock weak-lensing catalogs that directly incorporate the actual observational characteristics of the Canada-France-Hawaii Lensing Survey (CFHTLenS). We then perform a Fisher analysis using the large set of mock catalogs for various cosmological models. We find that the statistical error associated with the observational effects degrades the cosmological parameter constraints by a factor of a few. The Subaru Hyper Suprime-Cam (HSC) survey with a sky coverage of ~1400 deg2 will constrain the dark energy equation of the state parameter with an error of ?w 0 ~ 0.25 by the lensing MFs alone, but biases induced by the systematics can be comparable to the 1? error. We conclude that the lensing MFs are powerful statistics beyond the two-point statistics only if well-calibrated measurement of both the redshifts and the shapes of source galaxies is performed. Finally, we analyze the CFHTLenS data to explore the ability of the MFs to break degeneracies between a few cosmological parameters. Using a combined analysis of the MFs and the shear correlation function, we derive the matter density \\Omega _m0 = 0.256+/- ^{0.054}_{0.046}.
Shirasaki, Masato; Yoshida, Naoki
The 400d Galaxy Cluster Survey weak lensing programme. II. Weak lensing study of seven clusters with MMT/MegaCam
NASA Astrophysics Data System (ADS)
Context. Evolution in the mass function of galaxy clusters sensitively traces both the expansion history of the Universe and cosmological structure formation. Robust cluster mass determinations are a key ingredient for a reliable measurement of this evolution, especially at high redshift. Weak gravitational lensing is a promising tool for, on average, unbiased mass estimates. Aims: This weak lensing project aims at measuring reliable weak lensing masses for a complete X-ray selected sample of 36 high redshift (0.35 < z < 0.9) clusters. The goal of this paper is to demonstrate the robustness of the methodology against commonly encountered problems, including pure instrumental effects, the presence of bright (8-9 mag) stars close to the cluster centre, ground based measurements of high-z (z ~0.8) clusters, and the presence of massive unrelated structures along the line-sight. Methods: We select a subsample of seven clusters observed with MMT/MegaCam. Instrumental effects are checked in detail by cross-comparison with an archival CFHT/MegaCam observation. We derive mass estimates for seven clusters by modelling the tangential shear with an NFW profile, in two cases with multiple components to account for projected structures in the line-of-sight. Results: We firmly detect lensing signals from all seven clusters at more than 3.5? and determine their masses, ranging from 1014 M? to 1015 M?, despite the presence of nearby bright stars. We retrieve the lensing signal of more than one cluster in the CL 1701+6414 field, while apparently observing CL 1701+6414 through a massive foreground filament. We also find a multi-peaked shear signal in CL 1641+4001. Shear structures measured in the MMT and CFHT images of CL 1701+6414 are highly correlated. Conclusions: We confirm the capability of MMT/MegaCam to infer weak lensing masses from high-z clusters, demonstrated by the high level of consistency between MMT and CFHT results for CL 1701+6414. This shows that, when a sophisticated analysis is applied, instrumental effects are well under control. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona.Appendices are available in electronic form at http://www.aanda.orgReduced and coadded MMT image files are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/546/A79
Israel, H.; Erben, T.; Reiprich, T. H.; Vikhlinin, A.; Sarazin, C. L.; Schneider, P.
Catastrophic photometric redshift errors: weak-lensing survey requirements
NASA Astrophysics Data System (ADS)
We study the sensitivity of weak-lensing surveys to the effects of catastrophic redshift errors - cases where the true redshift is mis-estimated by a significant amount. To compute the biases in cosmological parameters, we adopt an efficient linearized analysis where the redshift errors are directly related to shifts in the weak-lensing convergence power spectra. We estimate the number Nspec of unbiased spectroscopic redshifts needed to determine the catastrophic error rate well enough that biases in cosmological parameters are below statistical errors of weak-lensing tomography. While the straightforward estimate of Nspec is ~106, we find that using only the photometric redshifts with z <~ 2.5 leads to a drastic reduction in Nspec to ~30000 while negligibly increasing statistical errors in dark-energy parameters. Therefore, the size of the spectroscopic survey needed to control catastrophic errors is similar to that previously deemed necessary to constrain the core of the zs-zp distribution. We also study the efficacy of the recent proposal to measure redshift errors by cross-correlation between the photo-z and spectroscopic samples. We find that this method requires ~10 per cent a priori knowledge of the bias and stochasticity of the outlier population, and is also easily confounded by lensing magnification bias. The cross-correlation method is therefore unlikely to supplant the need for a complete spectroscopic-redshift survey of the source population.
Bernstein, Gary; Huterer, Dragan
Non-linear relativistic contributions to the cosmological weak-lensing convergence
NASA Astrophysics Data System (ADS)
Relativistic contributions to the dynamics of structure formation come in a variety of forms, and can potentially give corrections to the standard picture on typical scales of 100 Mpc. These corrections cannot be obtained by Newtonian numerical simulations, so it is important to accurately estimate the magnitude of these relativistic effects. Density fluctuations couple to produce a background of gravitational waves, which is larger than any primordial background. A similar interaction produces a much larger spectrum of vector modes which represent the frame-dragging rotation of spacetime. These can change the metric at the percent level in the concordance model at scales below the equality scale. Vector modes modify the lensing of background galaxies by large-scale structure. This gives in principle the exciting possibility of measuring relativistic frame dragging effects on cosmological scales. The effects of the non-linear tensor and vector modes on the cosmic convergence are computed and compared to first-order lensing contributions from density fluctuations, Doppler lensing, and smaller Sachs-Wolfe effects. The lensing from gravitational waves is negligible so we concentrate on the vector modes. We show the relative importance of this for future surveys such as Euclid and SKA. We find that these non-linear effects only marginally affect the overall weak lensing signal so they can safely be neglected in most analyses, though are still much larger than the linear Sachs-Wolfe terms. The second-order vector contribution can dominate the first-order Doppler lensing term at moderate redshifts and are actually more important for survey geometries like the SKA.
Andrianomena, Sambatra; Clarkson, Chris; Patel, Prina; Umeh, Obinna; Uzan, Jean-Philippe
On cosmological gravitational lensing of classical gamma-ray bursts
NASA Astrophysics Data System (ADS)
It is argued that the most natural explanation of recent observations of gamma-ray bursts (GRBs) is that they are cosmological. Assuming that they are standard candles with no number or luminosity evolution in co-moving coordinates, the deficiency of faint GRBs observed by the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory can be successfully explained in the context of standard Friedmann-Lemaitre cosmological models. However, GRBs cannot distinguish among different cosmologies; the parameter space within which a successful theoretical model of the population of GRBs could be established is quite large. It is also not possible to say whether GRBs evolve or not. At any rate, the most simple, flat cosmological model fits the data very well The luminosity of a standard candle burst with no beaming is estimated to be approximately 1050erg/s. The average redshift of BATSE GRBs is estimated to be of the order of unity. An estimate of the contribution of GRBs to the diffuse gamma ray background yields an upper limit to the luminosity of a standard candle burst to be is less than 1054 erg/s. It is also concluded that the rate of GRBs in the entire observable universe should be approximately 3100 yr-1 if the source beaming is neglected BATSE GRBs have been searched for possible gravitational lensing. An analysis of 44 GRBs showed that none was lensed. This null result implies an exclusion of compact masses in the universe over the range 106.5 - 108.1 solar mass. The possibility of the determination of lens parameters from lensing of GRBs is discussed. A lensed GRB uniquely determines (1 + zd)M, where zd is the redshift of a compact mass lens of mass M. The mass determination via this method b accurate only up to a factor of 2 because usually the redshift of the lens is not observed. Theoretically, it is also possible to estimate the Hubble constant from lensing of GRBs. However, it is unlikely that present BATSE data will yield an accurate value because of the poor angular resolution of BATSE detectors; the determination of the Hubble constant is involved with the angular positions of images of a lensed GRB. As the second phase of the lens search, more than 600 GRBs were tested to see whether they had undergone gravitational lensing. This result was also null From this null result, the maximum redshift limit of BATSE GRBs was estimated to be approximately less than 2.4 - 6.2. The rate of discovering gravitationally lensed GRBs by BATSE was estimated to be one every S-24 years. The probability of lensing of GRBs as calculated from the null result of the lensing search is approximately 1%. Color-color diagrams (CCDs) have been introduced as a possible classification scheme for GRB spectra. The CCDs show that GRBs are consistent with a cosmological interpretation of GRBs and there is a high degree of diversity among their spectra. The construction of a theoretical grid on CCDs is found to be an efficient way to identify spectra with different shapes.
Wickramasinghe, W. A. D. Thulsi
The Optical Gravitational Lensing Experiment (OGLE)
NASA Astrophysics Data System (ADS)
We continue observing microlensing events towards the Galactic bulge. The analysis of the first three years of the OGLE data revealed 12 microlensing events of the Galactic bulge stars, including first ever observed case of the microlensing by a binary star and first ever microlensing event discovered and observed in real time. A complete sample of nine events observed in 1992 and 1993 gave the optical depth to gravitational microlensing larger than (3.3 +/- 1.2) times 10(-6) , higher than expected. There is a number of side projects utilizing the data collected for the microlensing search. The OGLE color magnitude diagrams reveal the presence of the Galactic bar and a low density inner disk region ~ 4 kpc in radius. First two parts of the catalogue of a few thousand variable stars were published and are available over the computer network. When the Galactic bulge could not be observed we had a number of secondary targets. In 1993 one field in Sculptor dwarf galaxy was monitored and over 200 RR Lyrae stars were detected. Also, two globular clusters, 47 Tuc and Omega Cen, were monitored in 1993 and 1994 in a search for detached eclipsing binaries. So far three such systems were found in Omega Cen. In 1994 one field in the recently discovered Sagittarius dwarf galaxy was observed. We detected seven RR Lyrae variables belonging to the dwarf. The dedicated, 1.3-m OGLE telescope is under construction on the Las Campanas site. The first light is expected by the Fall 1995. The up-to-date information on the OGLE project, including catalogs of the variable stars is accessible over the Internet network from sirius.astrouw.edu.pl host (18.104.22.168), using the ``anonymous ftp'' service (directory ogle). The OGLE results are also available over the WWW at : http://www.astrouw.edu.pl/\\ udalski/ogle.html.
Stanek, K. Z.; Paczynski, B.; Udalski, A.; Szymanski, M.; Uzny, J. Ka\\L.; Kubiak, M.; Mateo, M.; Krzeminski, W.; Preston, G. W.
Constraining fast radio burst progenitors with gravitational lensing
NASA Astrophysics Data System (ADS)
Fast Radio Bursts (FRBs) are new transient radio sources discovered recently. Because of the angular resolution restriction in radio surveys, no optical counter part has been identified yet so it is hard to determine the progenitor of FRBs. In this paper we propose to use radio lensing survey to constrain FRB progenitors. We show that, different types of progenitors lead to different probabilities for a FRB to be gravitationally lensed by dark matter halos in foreground galaxies, since different type progenitors result in different redshift distributions of FRBs. For example, the redshift distribution of FRBs arising from double stars shifts toward lower redshift than of the FRBs arising from single stars, because double stars and single stars have different evolution timescales. With detailed calculations, we predict that the FRB sample size for producing one lensing event varies significantly for different FRB progenitor models. We argue that this fact can be used to distinguish different FRB models and also discuss the practical possibility of using lensing observation in radio surveys to constrain FRB progenitors.
Li, ChunYu; Li, LiXin
Constraining fast radio burst progenitors with gravitational lensing
NASA Astrophysics Data System (ADS)
Fast Radio Bursts (FRBs) are new transient radio sources discovered recently. Because of the angular resolution restriction in radio surveys, no optical counter part has been identified yet so it is hard to determine the progenitor of FRBs. In this paper we propose to use radio lensing survey to constrain FRB progenitors. We show that, different types of progenitors lead to different probabilities for a FRB to be gravitationally lensed by dark matter halos in foreground galaxies, since different type progenitors result in different redshift distributions of FRBs. For example, the redshift distribution of FRBs arising from double stars shifts toward lower redshift than of the FRBs arising from single stars, because double stars and single stars have different evolution timescales. With detailed calculations, we predict that the FRB sample size for producing one lensing event varies significantly for different FRB progenitor models. We argue that this fact can be used to distinguish different FRB models and also discuss the practical possibility of using lensing observation in radio surveys to constrain FRB progenitors.
Li, ChunYu; Li, LiXin
How to Measure Dark Energy with LSST's Strong Gravitational Lenses
NASA Astrophysics Data System (ADS)
Strong gravitational lensing is sensitive to dark energy (DE) via the combinations of angular diameter distances that appear in model predictions of the lens strength. Lenses with variable sources offer the most promise: the corresponding time delay distance has recently been shown to be measurable to 5% precision. Large samples of lensed quasars and supernovae will allow internal degeneracy-breaking and so enable the most direct access to the DE parameters, while multiple source-plane, compound lens systems may provide an alternative, complementary, H0-free probe. Its wide field survey and high cadence will enable LSST to provide a sample of several thousand measured time delays, two orders of magnitude larger than the current sample, and allow an independent, competitive Stage IV DE parameter measurement to be made. However, practical problems to be solved include: lens detection (which may be very sensitive to image quality and deblender performance); image and lightcurve modelling (which could be both CPU and manual labor-intensive); obtaining and analyzing high resolution spectro-imaging follow-up data; and interpreting the whole sample of lenses in the context of the well-studied subset.
Marshall, Philip J.; Treu, T.; Brunner, R. J.; Strong Lensing, LSST; Dark Energy Science Collaborations
Accurate weak lensing of standard candles. I. Flexible cosmological fits
NASA Astrophysics Data System (ADS)
With the availability of thousands of type Ia supernovae in the near future the magnitude scatter induced by lensing will become a major issue as it affects parameter estimation. Current N-body simulations are too time consuming to be integrated in the likelihood analyses used for estimating the cosmological parameters. In this paper we show that in the weak-lensing regime a statistical numerical approximation produces accurate results orders of magnitude faster. We write down simple fits to the second, third and fourth central moments of the lensing magnification probability distribution as a function of redshift, of the power spectrum normalization and of the present-day matter density. We also improve upon existing models of lensing variance and show that a shifted log-normal distribution fits well the numerical one. These fits can be easily employed in cosmological likelihood analyses. Moreover, our theoretical predictions make it possible to invert the problem and begin using supernovae lensing to constrain the cosmological parameters.
Marra, Valerio; Quartin, Miguel; Amendola, Luca
Gravitational Lensing and the Geometry of the Universe
NASA Astrophysics Data System (ADS)
New and improved data on the gravitational lens systems discovered so far are compared with the theoretical predictions of Gott, Park and Lee(1989, GPL). Systems lensed by a single galaxy, compatible with assumptions of GPL, support flat or near-flat geometry for the universe. But the statistical uncertainty is too large to draw any definite conclusion. We need more lens systems. Also, the probability of multiple image lensing and mean separation of the images averaged over the source distribution are calculated for various cosmological models. Multiple-image lens systems and radio ring systems are compared with predictions. Although the data reject exotic cosmological models, it cannot discriminate among conventional Friedmann models yet.
Park, Myeong-Gu
Discovery of a Gravitationally Lensed Type Ia Supernova
NASA Astrophysics Data System (ADS)
Recently, Pan-STARRS detected an unusual optical transient named PS1-10afx. While it has been argued PS1-10afx is a new type of superluminous supernova, we find that it is, in fact, a normal Type Ia supernova: its spectra are well matched by normal Type Ia exemplars such as SN 1994D, and its photometry has the colors and light curve shape expected for a Type Ia supernova at z=1.39; however, it is some 3.7 magnitudes too bright. We show that this excess brightness is caused by the gravitational lensing of the supernova by a foreground object, and we present new observations revealing the nature of this lensing object.
Quimby, Robert
Effects of supermassive binary black holes on gravitational lenses
NASA Astrophysics Data System (ADS)
Recent observations indicate that many, if not all, galaxies host massive central black holes (BHs). In this paper, we explore the influence of supermassive binary black holes (SMBBHs) on their actions as gravitational lenses. When lenses are modelled as singular isothermal ellipsoids, binary BHs change the critical curves and caustics differently as a function of distance. Each BH can in principle create at least one additional image, which, if observed, provides evidence of BHs. By studying how SMBBHs affect the cumulative distribution of magnification for images created by BHs, we find that the cross-section for at least one such additional image to have a magnification larger than 10-5 is comparable to the cross-section for producing multiple images in singular isothermal lenses. Such additional images may be detectable with high-resolution and large dynamic range maps of multiply imaged systems from future facilities, such as the Square Kilometre Array. The probability of detecting at least one image (two images) with magnification above 10-3 is �0.2fBH (�0.05fBH) in a multiply imaged lens system, where fBH is the fraction of galaxies housing binary BHs. We also study the effects of SMBBHs on the core images when galaxies have shallower central density profiles (modelled as non-singular isothermal ellipsoids). We find that the cross-section of the usually faint core images is further suppressed by SMBBHs. Thus, their presence should also be taken into account when one constrains the core radius from the lack of central images in gravitational lenses.
Li, Nan; Mao, Shude; Gao, Liang; Loeb, Abraham; di Stefano, R.
The image jets modeling of gravitationally lensed sources
NASA Astrophysics Data System (ADS)
The jets image modelling of gravitationally lensed sources have been performed. Several basic models of the lens mass distribution were considered, in particular, a singular isothermal ellipsoid, an isothermal ellipsoid with the core, different multi-components models with the galactic disk, halo and bulge. The obtained jet images were compared as with each other as with results of observations. A significant dependence of the Hubble constant on the model parameters was revealed for B0218+357, when the circular structure was took into account.
Larchenkova, Tatiana; Lutovinov, Alexander; Lyskova, Natalya
A note on a linearized approach to gravitational lensing
NASA Astrophysics Data System (ADS)
A recent paper by Walters, Forbes and Jarvis presented new kinematic formulae for ray tracing in gravitational lensing models. The approach can generate caustic maps, but is computationally expensive. Here, a linearized approximation to that formulation is presented. Although still complicated, the linearized equations admit a remarkable closed-form solution. As a result, linearized approximations to the caustic patterns may be generated extremely rapidly, and are found to be in good agreement with the results of full non-linear computation. The usual Einstein-angle approximation is derived as a small angle approximation to the solution presented here.
Walters, S. J.; Forbes, L. K.
Wide-field weak lensing by RXJ1347-1145
NASA Astrophysics Data System (ADS)
We present an analysis of weak lensing observations for RXJ1347--1145 over a 43 ' � 43 ' field taken in B and R filters on the Blanco 4m telescope at CTIO. RXJ1347--1145 is a massive cluster at redshift z=0.45. Using a population of galaxies with 20
Kling, Thomas P.; dell'Antonio, Ian; Wittman, David; Tyson, J. Anthony
GRAVITATIONAL LENSING CORRECTIONS IN FLAT {Lambda}CDM COSMOLOGY
We compute the deflection angle to order (m/r {sub 0}){sup 2} and m/r{sub 0} x {Lambda}r {sup 2}{sub 0} for a light ray traveling in a flat {Lambda}CDM cosmology that encounters a completely condensed mass region. We use a Swiss cheese model for the inhomogeneities and find that the most significant correction to the Einstein angle occurs not because of the nonlinear terms but instead occurs because the condensed mass is embedded in a background cosmology. The Swiss cheese model predicts a decrease in the deflection angle of {approx}2% for weakly lensed galaxies behind the rich cluster A1689 and that the reduction can be as large as {approx}5% for similar rich clusters at z {approx} 1. Weak-lensing deflection angles caused by galaxies can likewise be reduced by as much as {approx}4%. We show that the lowest order correction in which {Lambda} appears is proportional to m/r{sub 0} x {radical}({Lambda}r{sub 0}{sup 2}) and could cause as much as a {approx}0.02% increase in the deflection angle for light that passes through a rich cluster. The lowest order nonlinear correction in the mass is proportional to m/r{sub 0}x{radical}(m/r{sub 0}) and can increase the deflection angle by {approx}0.005% for weak lensing by galaxies.
Kantowski, Ronald; Chen Bin; Dai Xinyu, E-mail: firstname.lastname@example.com, E-mail: email@example.com, E-mail: firstname.lastname@example.com [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States)
The upcoming new generation of spectroscopic galaxy redshift surveys will provide large samples of cosmic voids, large distinct, underdense structures in the universe. Combining these with future galaxy imaging surveys, we study the prospects of probing the underlying matter distribution in and around cosmic voids via the weak gravitational lensing effects of stacked voids, utilizing both shear and magnification information. The statistical precision is greatly improved by stacking a large number of voids along different lines of sight, even when taking into account the impact of inherent miscentering and projection effects. We show that Dark Energy Task Force Stage IV surveys, such as the Euclid satellite and the Large Synoptic Survey Telescope, should be able to detect the void lensing signal with sufficient precision from stacking abundant medium-sized voids, thus providing direct constraints on the matter density profile of voids independent of assumptions on galaxy bias.
Krause, Elisabeth; Dore, Olivier [Department of Astrophysics, Caltech, MC 249-17, Pasadena, CA 91125 (United States); Chang, Tzu-Ching; Umetsu, Keiichi [IAA, Academia Sinica, P.O. Box 23-141, Taipei 10617, Taiwan (China)
A gravitationally lensed water maser in the early Universe.
Water masers are found in dense molecular clouds closely associated with supermassive black holes at the centres of active galaxies. On the basis of the understanding of the local water-maser luminosity function, it was expected that masers at intermediate and high redshifts would be extremely rare. However, galaxies at redshifts z > 2 might be quite different from those found locally, not least because of more frequent mergers and interaction events. Here we use gravitational lensing to search for masers at higher redshifts than would otherwise be possible, and find a water maser at redshift 2.64 in the dust- and gas-rich, gravitationally lensed type-1 quasar MG J0414+0534 (refs 6-13). The isotropic luminosity is 10,000 (, solar luminosity), which is twice that of the most powerful local water maser and half that of the most distant maser previously known. Using the locally determined luminosity function, the probability of finding a maser this luminous associated with any single active galaxy is 10(-6). The fact that we see such a maser in the first galaxy we observe must mean that the volume densities and luminosities of masers are higher at redshift 2.64. PMID:19092930
Impellizzeri, C M Violette; McKean, John P; Castangia, Paola; Roy, Alan L; Henkel, Christian; Brunthaler, Andreas; Wucknitz, Olaf
We present Chandra monitoring data for six gravitationally lensed quasars: QJ 0158-4325, HE 0435-1223, SDSS 0924+0219, SDSS 1004+4112, HE 1104-1805, and Q 2237+0305. X-ray microlensing variability is detected in all six lenses with high confidence. We furthermore detect energy-dependent microlensing in HE 0435-1223, SDSS 0924+0219, SDSS 1004+4112, and Q 2237+0305. Through a detailed spectral analysis for each lens we find that simple power-law models plus Gaussian emission lines give good fits to the spectra. We detect intrinsic spectral variability in two epochs of Q 2237+0305, and differential absorption between images in QJ 0158-4325 and Q2237+0305. We also detect the Fe K{alpha} emission line in all six lenses, and the Ni XXVII K{alpha} line in two images of Q 2237+0305. The rest-frame equivalent widths of the Fe K{alpha} lines are measured to be 0.4-1.2 keV, significantly higher than those measured in typical active galactic nuclei of similar X-ray luminosities. This suggests that the Fe K{alpha} emission region is more compact or centrally concentrated than the continuum emission region.
Chen Bin; Dai Xinyu [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK 73019 (United States); Kochanek, Christopher S.; Blackburne, Jeffrey A. [Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States); Chartas, George [Department of Physics and Astronomy, College of Charleston, SC 29424 (United States); Morgan, Christopher W., E-mail: email@example.com [Department of Physics, United States Naval Academy, 572C Holloway Road, Annapolis, MD 21402 (United States)
CFHTLenS: The Environmental Dependence of Galaxy Halo Masses from Weak Lensing
NASA Astrophysics Data System (ADS)
We use weak gravitational lensing to analyse the dark matter halos around satellite galaxies in galaxy groups in the CFHTLenS dataset. This dataset is derived from the CFHTLS-Wide survey, and encompasses 154 sq. deg of high-quality shape data. Using the photometric redshifts, we divide the sample of lens galaxies with stellar masses in the range 10^9 Msun to 10^10.5 Msun into those likely to lie in high-density environments (HDE) and those likely to lie in low-density environments (LDE). Through comparison with galaxy catalogues extracted from the Millennium Simulation, we show that the sample of HDE galaxies should primarily 61%) consist of satellite galaxies in groups, while the sample of LDE galaxies should consist of mostly 87%) non-satellite (field and central) galaxies. Comparing the lensing signals around samples of HDE and LDE galaxies matched in stellar mass, the lensing signal around HDE galaxies clearly shows a positive contribution from their host groups on their lensing signals at radii of ~500--1000 kpc, the typical separation between satellites and group centres. More importantly, the subhalos of HDE galaxies are less massive than those around LDE galaxies by a factor 0.65 +/- 0.12, significant at the 2.9 sigma level. A natural explanation is that the halos of satellite galaxies are stripped through tidal effects in the group environment. Our results are consistent with a typical tidal truncation radius of ~40 kpc.
Gillis, Bryan; Hudson, M. J.; Erben, T.; Heymans, C.; Hildebrandt, H.; Hoekstra, H.; Kitching, T. D.; Mellier, Y.; Miller, L.; van Waerbeke, L.; Bonnett, C.; Coupon, J.; Fu, L.; Hilbert, S.; Rowe, B.; Schrabback, T.; Semboloni, E.; van Uitert, E.; Velander, M.; Cfhtlens Team
Weak lensing survey of galaxy clusters in the CFHTLS Deep
NASA Astrophysics Data System (ADS)
Aims: We present a weak lensing search of galaxy clusters in the 4 deg2 of the CFHT Legacy Survey Deep. This work aims at building a mass-selected sample of clusters with well controlled selection effects. This present survey is a preliminary step toward a full implementation in the forthcoming 170 deg2 of the CFHTLS Wide survey. Methods: We use the deep i' band images observed under subarcsecond seeing conditions to perform weak lensing mass reconstructions and to identify high convergence peaks. Thanks to the availability of deep u^*g'r'i'z' exposures, sources are selected from their photometric redshifts in the weak lensing analysis. We also use lensing tomography to derive an estimate of the lens redshift. After considering the raw statistics of peaks we check whether they can be associated to a clear optical counterpart or to published X-ray selected clusters. Results: Among the 14 peaks found above a signal-to-noise detection threshold ?=3.5, nine are secure detections with estimated redshift 0.1? z_l?0.7 and a velocity dispersion 450??_v? 700 {km s}-1. This low mass range is accessible thanks to the high density of background sources. Considering the intersection between the shear-selected clusters and XMM-LSS X-ray clusters in the D1 field, we observe that the ICM gas in these low-mass clusters (T_X�1{-}2 keV) is not hotter than the temperature inferred from shear, this trend being different for published massive clusters. A more extended weak lensing survey, with higher statistics of mass structures will be a promising way to bypass several of the problems related to standard detection methods based on the complex physics of baryons. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.
Gavazzi, R.; Soucail, G.
Unveiling shapes: Shapelets for galaxy morphology and gravitational lensing studies
NASA Astrophysics Data System (ADS)
The shapelet basis system forms a convenient and mathematically well-established framework for describing shapes of galaxies and the telescope's point spread function (PSF). A shapelet-based image processing pipeline thus offers remarkable benefits: For weak-lensing studies, its analytic and efficient deconvolution procedure from arbitrary PSFs constitutes a significant improvement on the traditional KSB method. For complex morphologies of the lensed galaxy ensemble, it has proven to belong to the most accurate shear measurement methods available today. Furthermore, a multitude of shear estimators can be formed from the expansion coefficients, which allows cross-checking of measurements. For statistical investigation of galaxy morphologies, one profits from the significant dimensionality reduction and scale-invariance provided by the shapelet decomposition. Unfortunately, overfitting the data and unphysical high-frequency oscillations pose apparent limitations to its applicability. These problems can be remedied by minor modifications to the decomposition and deconvolution procedures.
Melchior, Peter
Three Gravitational Lenses for the Price of One: Enhanced Strong Lensing Through Galaxy Clustering
We report the serendipitous discovery of two strong gravitational lens candidates (ACS J160919+6532 and ACS J160910+6532) in deep images obtained with the Advanced Camera for Surveys on the Hubble Space Telescope, each less than 40'' from the previously known gravitational lens system CLASS B1608+656. The redshifts of both lens galaxies have been measured with Keck and Gemini: one is a member of a small galaxy group at z {approx} 0.63, which also includes the lensing galaxy in the B1608+656 system, and the second is a member of a foreground group at z {approx} 0.43. By measuring the effective radii and surface brightnesses of the two lens galaxies, we infer their velocity dispersions based on the passively evolving Fundamental Plane (FP) relation. Elliptical isothermal lens mass models are able to explain their image configurations within the lens hypothesis, with a velocity dispersion compatible with that estimated from the FP for a reasonable source-redshift range. Based on the large number of massive early-type galaxies in the field and the number-density of faint blue galaxies, the presence of two additional lens systems around CLASS B1608+656 is not unlikely in hindsight. Gravitational lens galaxies are predominantly early-type galaxies, which are clustered, and the lensed quasar host galaxies are also clustered. Therefore, obtaining deep high-resolution images of the fields around known strong lens systems is an excellent method of enhancing the probability of finding additional strong gravitational lens systems.
Fassnacht, Chris D.; McKean, J.P.; Koopmans, L.V.E.; Treu, T.; Blandford, R.D.; Auger, M.W.; Jeltema, T.E.; Lubin, L.M.; Margoniner, V.E.; Wittman, D.; /UC, Davis /Kapteyn Astron. Inst., Groningen /UC, Santa Barbara /KIPAC, Menlo Park /Carnegie Inst. Observ.
Intrinsic ellipticity correlations of galaxies: models, likelihoods and interplay with weak lensing
NASA Astrophysics Data System (ADS)
Subject of this paper is the statistical properties of ellipticity alignments between galaxies evoked by their coupled angular momenta. Starting from physical angular momentum models, we bridge the gap towards ellipticity correlations, ellipticity spectra and derived quantities such as aperture moments, comparing the intrinsic signals with those generated by gravitational lensing, with the projected galaxy sample of Euclid in mind. We investigate the dependence of intrinsic ellipticity correlations on cosmological parameters and show that intrinsic ellipticity correlations give rise to non-Gaussian likelihoods as a result of non-linear functional dependences. Comparing intrinsic ellipticity spectra to weak lensing spectra we quantify the magnitude of their contaminating effect on the estimation of cosmological parameters and find that biases on dark energy parameters are very small in an angular momentum-based model in contrast to the linear alignment model commonly used. Finally, we quantify whether intrinsic ellipticities can be measured in the presence of the much stronger weak lensing induced ellipticity correlations, if prior knowledge on a cosmological model is assumed.
Capranico, Federica; Merkel, Philipp M.; Sch�fer, Bj�rn Malte
A Bayesian Analysis of Regularised Source Inversions in Gravitational Lensing
Strong gravitational lens systems with extended sources are of special interest because they provide additional constraints on the models of the lens systems. To use a gravitational lens system for measuring the Hubble constant, one would need to determine the lens potential and the source intensity distribution simultaneously. A linear inversion method to reconstruct a pixellated source distribution of a given lens potential model was introduced by Warren and Dye. In the inversion process, a regularization on the source intensity is often needed to ensure a successful inversion with a faithful resulting source. In this paper, we use Bayesian analysis to determine the optimal regularization constant (strength of regularization) of a given form of regularization and to objectively choose the optimal form of regularization given a selection of regularizations. We consider and compare quantitatively three different forms of regularization previously described in the literature for source inversions in gravitational lensing: zeroth-order, gradient and curvature. We use simulated data with the exact lens potential to demonstrate the method. We find that the preferred form of regularization depends on the nature of the source distribution.
Suyu, Sherry H.; /Caltech /KIPAC, Menlo Park; Marshall, P.J.; /KIPAC, Menlo Park; Hobson, M.P.; /Cambridge U., Inst. of Astron.; Blandford, R.D.; /Caltech /KIPAC, Menlo Park
Method to measure a relative transverse velocity of a source-lens-observer system using gravitational lensing of gravitational waves
Gravitational waves propagate along null geodesics like light rays in the geometrical optics approximation, and they may have a chance to suffer from gravitational lensing by intervening objects, as is the case for electromagnetic waves. Long wavelengths of gravitational waves and compactness of possible sources may enable us to extract information in the interference among the lensed images. We point out that the interference term contains information of relative transverse velocity of the source-lens-observer system, which may be obtained by possible future space-borne gravitational wave detectors such as BBO/DECIGO.
Itoh, Yousuke; Futamase, Toshifumi; Hattori, Makoto [Astronomical Institute, Graduate School of Science, Tohoku University, Sendai 980-8578 (Japan)
Direct measurement of the magnification produced by galaxy clusters as gravitational lenses
NASA Astrophysics Data System (ADS)
Context. Weak lensing is one of the most readily available diagnostic tools to measure the total density profiles of distant clusters of galaxies. Unfortunately, it suffers from the well-known mass-sheet degeneracy, so that weak lensing analyses cannot lead to fully reliable determinations of the total mass of the clusters. One possible way to set the relevant scale of the density profile would be to make a direct measurement of the magnification produced by the clusters as gravitational lenses; in the past, this objective has been addressed in a number of ways, but with no significant success. Aims: We revisit a suggestion made a few years ago for this general purpose, based on the use of the fundamental plane as a standard rod for early-type galaxies. Here we move one step further, beyond the simple outline of the idea given earlier, and quantify some statistical properties of this innovative diagnostic tool, with the final goal of identifying clear guidelines for a future observational test of concrete cases, which turns out to be well within the current instrument capabilities. Methods: The study is carried out by discussing the statistical properties of fundamental plane measurements for a sample of early-type source galaxies behind a massive cluster, for which a weak lensing analysis is assumed to be available. Some general results are first obtained analytically and then tested and extended by means of dedicated simulations. Results: We proceed with determining the optimal way of using fundamental plane measurements to determine the mass scale of a given cluster, which we find to be the study of a sample of early-type galaxies behind the cluster distributed approximately uniformly on the sky. We discuss the role of the redshift distribution of the source galaxies, in relation to the redshift of the lensing cluster and to the limitations of fundamental plane measurements. Simple simulations are carried out for clusters with intrinsic properties similar to those of the Coma cluster. We also show that, within a realistic cosmological scenario, substructures do not contribute much to the magnification signal that we are looking for, but add only a modest amount of scatter. Conclusions: We find that for a massive cluster (M200 > 1015 M?) located at redshift 0.3 � 0.1, a set of about 20 fundamental plane measurements, combined with a robust weak lensing analysis, should be able to lead to a mass determination with a precision of 20% or better.
Sonnenfeld, A.; Bertin, G.; Lombardi, M.
Strong and Weak Lensing United. III. Measuring the Mass Distribution of the Merging Galaxy Cluster 1ES 0657-558
The galaxy cluster 1ES 0657-558 (z=0.296) is remarkably well suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multicolor, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known
Marusa Bradac; Douglas Clowe; Anthony H. Gonzalez; Phil Marshall; William Forman; Christine Jones; Maxim Markevitch; Scott Randall; Tim Schrabback; Dennis Zaritsky
Fast calculation of the weak lensing aperture mass statistic
NASA Astrophysics Data System (ADS)
The aperture mass statistic is a common tool used in weak lensing studies. By convolving lensing maps with a filter function of a specific scale, chosen to be larger than the scale on which the noise is dominant, the lensing signal may be boosted with respect to the noise. This allows for detection of structures at increased fidelity. Furthermore, higher order statistics of the aperture mass (such as its skewness or kurtosis), or counting of the peaks seen in the resulting aperture mass maps, provide a convenient and effective method to constrain the cosmological parameters. In this paper, we more fully explore the formalism underlying the aperture mass statistic. We demonstrate that the aperture mass statistic is formally identical to a wavelet transform at a specific scale. Further, we show that the filter functions most frequently used in aperture mass studies are not ideal, being non-local in both real and Fourier space. In contrast, the wavelet formalism offers a number of wavelet functions that are localized both in real and Fourier space, yet similar to the optimal aperture mass filters commonly adopted. Additionally, for a number of wavelet functions, such as the starlet wavelet, very fast algorithms exist to compute the wavelet transform. This offers significant advantages over the usual aperture mass algorithm when it comes to image processing time, demonstrating speed-up factors of �5-1200 for aperture radii in the range 2-64 pixels on an image of 1024 � 1024 pixels.
Leonard, Adrienne; Pires, Sandrine; Starck, Jean-Luc
Cosmological Parameter Survey Using the Gravitational Lensing Method
NASA Astrophysics Data System (ADS)
Using a multiple-lens plane algorithm, we study light propagation in inhomogeneous universes for 43 different COBE-normalized Cold Dark Matter models, with various values of the density parameter ?0, cosmological constant ?0, Hubble constant H0, and rms density fluctuation ?8. We performed a total of 3798 experiments, each experiment consisting of propagating a square beam of angular size 21.9'' � 21.9'' composed of 116 281 light rays from the observer up to redshift z = 3. These experiments provide statis-tics of the magnification, shear, and multiple imaging of distant sources. The results of these experiments might be compared with observations, and eventually help constrain the possible values of the cosmological parameters. Additionally, they provide insight into the gravitational lensing process and its complex relationship with the various cosmological parameters.
Premadi, Premana W.; Martel, Hugo; Matzner, Richard; Futamase, Toshifumi
Seeing the Invisible Universe with Gravitational Lensing and SNAP
Recent high-precision cosmological measurements provide solid evidence that normal matter comprises only 4% of the content of the Universe. The dominant substances are completely invisible and have never been detected in a laboratory: 23% in some 'dark matter' particles, and 73% in a form of 'dark energy' that is currently accelerating the expansion of the Universe. The dark matter and dark energy do, however, distort our view of the Universe behind them through gravitational lensing, just as the 'obscure glass' on the doors of a shower stall is designed to be transparent but produces a distorted view of its occupant. I will describe how present and future experiments such as the SNAP spacecraft can measure this very subtle distorting effect and use it to infer the properties of the dark matter and dark energy that dominate the Universe.
Herschel-ATLAS: modelling the first strong gravitational lenses
NASA Astrophysics Data System (ADS)
We have determined the mass density radial profiles of the first five strong gravitational lens systems discovered by the Herschel Astrophysical Terahertz Large Area Survey. We present an enhancement of the semilinear lens inversion method of Warren & Dye which allows simultaneous reconstruction of several different wavebands and apply this to dual-band imaging of the lenses acquired with the Hubble Space Telescope. The five systems analysed here have lens redshifts which span a range 0.22 ? z ? 0.94. Our findings are consistent with other studies by concluding that: (1) the logarithmic slope of the total mass density profile steepens with decreasing redshift; (2) the slope is positively correlated with the average total projected mass density of the lens contained within half the effective radius and negatively correlated with the effective radius; (3) the fraction of dark matter contained within half the effective radius increases with increasing effective radius and increases with redshift.
Dye, S.; Negrello, M.; Hopwood, R.; Nightingale, J. W.; Bussmann, R. S.; Amber, S.; Bourne, N.; Cooray, A.; Dariush, A.; Dunne, L.; Eales, S. A.; Gonzalez-Nuevo, J.; Ibar, E.; Ivison, R. J.; Maddox, S.; Valiante, E.; Smith, M.
Three quasi-stellar objects acting as strong gravitational lenses
NASA Astrophysics Data System (ADS)
We report the discovery of three new cases of quasi-stellar objects (QSOs) acting as strong gravitational lenses on background emission line galaxies: SDSS J0827+5224 (zQSO = 0.293, zs = 0.412), SDSS J0919+2720 (zQSO = 0.209, zs = 0.558), SDSS J1005+4016 (zQSO = 0.230, zs = 0.441). The selection was carried out using a sample of 22,298 SDSS spectra displaying at least four emission lines at a redshift beyond that of the foreground QSO. The lensing nature is confirmed from Keck imaging and spectroscopy, as well as from HST/WFC3 imaging in the F475W and F814W filters. Two of the QSOs have face-on spiral host galaxies and the third is a QSO+galaxy pair. The velocity dispersion of the host galaxies, inferred from simple lens modeling, is between ? = 210 and 285 km s-1, making these host galaxies comparable in mass with the SLACS sample of early-type strong lenses. Based on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Also based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program #GO12233.
Courbin, F.; Faure, C.; Djorgovski, S. G.; R�rat, F.; Tewes, M.; Meylan, G.; Stern, D.; Mahabal, A.; Boroson, T.; Dheeraj, R.; Sluse, D.
Constraints on Galaxy Evolution Through Gravitational Lensing Statistics
NASA Astrophysics Data System (ADS)
Explaining the formation and evolution of galaxies is one of the most challenging problems in observational cosmology. Many observations suggest that galaxies we see today could have evolved from the merging of smaller subsystems. Evolution of galaxies tells us how the mass or number density of the lens varies with cosmic time. Merging between the galaxies and the infall of surrounding mass into galaxies are two possible processes that can change the comoving number density of galaxies and/or their mass. We consider five different evolutionary models of galaxies. These models are: Non-evolutionary model, Guiderdoni and Volmerange model, fast merging, slow merging and mass accretion model. We study the gravitational lens image separation distribution function for these models of evolving galaxies. A comparison with data for lensed quasars taken from the HST snapshot survey rules out the fast merging model completely as this model produces a large number of small-separation lenses. It is possible that the mass accretion model and the non-evolutionary model of galaxies may be able to explain the small angle separations.
Jain, Deepak; Panchapakesan, N.; Mahajan, S.; Bhatia, V. B.
Gravitational lensing by a collection of objects with radial densities
NASA Astrophysics Data System (ADS)
In a recent paper by Bayer et al. (Gen Rel Grav 38:1379-1385, 2006), the authors considered a certain class of gravitational lenses consisting of n non-overlapping objects with radial densities. They concluded that there can be at most 6( n - 1) + 1 lensed images of a single light source. The only assumption made on the projected mass density of each object is that it is radial and does not diverge faster than 1/ r, where r is the distance to the center of the object. We show that this is too general a class of densities to consider while imposing a bound of 6( n - 1) + 1. We also provide an example to emphasize [together with the results in Bayer et al. (Gen Rel Grav 38:1379-1385, 2006)] that the general problem of finding the correct hypothesis to obtain sharp bounds for the maximal number of images inside the region occupied by masses with radial densities is wide open.
Khavinson, Dmitry; Lundberg, Erik
We have worked out simple analytical formulae that accurately approximate the relationship between the position of the source with respect to the lens center and the amplification of the images, hence the lens cross section, for realistic lens profiles. We find that, for essentially the full range of parameters either observationally determined or yielded by numerical simulations, the combination of dark matter and star distribution can be very well described, for lens radii relevant to strong lensing, by a simple power law whose slope is very weakly dependent on the parameters characterizing the global matter surface density profile and close to isothermal in agreement with direct estimates for individual lens galaxies. Our simple treatment allows an easy insight into the role of the different ingredients that determine the lens cross section and the distribution of gravitational amplifications. They also ease the reconstruction of the lens mass distribution from the observed images and, vice versa, allow a fast application of ray-tracing techniques to model the effect of lensing on a variety of source structures. The maximum amplification depends primarily on the source size. Amplifications larger than Almost-Equal-To 20 are indicative of compact source sizes at high-z, in agreement with expectations if galaxies formed most of their stars during the dissipative collapse of cold gas. Our formalism has allowed us to reproduce the counts of strongly lensed galaxies found in the H-ATLAS Science Demonstration Phase field. While our analysis is focused on spherical lenses, we also discuss the effect of ellipticity and the case of late-type lenses (showing why they are much less common, even though late-type galaxies are more numerous). Furthermore, we discuss the effect of a cluster halo surrounding the early-type lens and of a supermassive black hole at its center.
Lapi, A. [Dipartimento Fisica, Universita 'Tor Vergata', Via Ricerca Scientifica 1, 00133 Roma (Italy); Negrello, M. [INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova (Italy); Gonzalez-Nuevo, J.; Cai, Z.-Y.; De Zotti, G.; Danese, L. [Astrophysics Sector, SISSA, Via Bonomea 265, 34136 Trieste (Italy)
Gravitational lensing: a unique probe of dark matter and dark energy
I review the development of gravitational lensing as a powerful tool of the observational cosmologist. After the historic eclipse expedition organized by Arthur Eddington and Frank Dyson, the subject lay observationally dormant for 60 years. However, subsequent progress has been astonishingly rapid, especially in the past decade, so that gravitational lensing now holds the key to unravelling the two most profound mysteries of our Universe�the nature and distribution of dark matter, and the origin of the puzzling cosmic acceleration first identified in the late 1990s. In this non-specialist review, I focus on the unusual history and achievements of gravitational lensing and its future observational prospects.
Ellis, Richard S.
Gravitational lensing: a unique probe of dark matter and dark energy.
I review the development of gravitational lensing as a powerful tool of the observational cosmologist. After the historic eclipse expedition organized by Arthur Eddington and Frank Dyson, the subject lay observationally dormant for 60 years. However, subsequent progress has been astonishingly rapid, especially in the past decade, so that gravitational lensing now holds the key to unravelling the two most profound mysteries of our Universe-the nature and distribution of dark matter, and the origin of the puzzling cosmic acceleration first identified in the late 1990s. In this non-specialist review, I focus on the unusual history and achievements of gravitational lensing and its future observational prospects. PMID:20123743
Ellis, Richard S
Weak Lensing Measurement of Galaxy Clusters in the CFHTLS-Wide Survey
NASA Astrophysics Data System (ADS)
We present the first weak gravitational lensing analysis of the completed Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We study the 64 deg2 W1 field, the largest of the CFHTLS-Wide survey fields, and present the largest contiguous weak lensing convergence "mass map" yet made. 2.66 million galaxy shapes are measured, using the Kaiser Squires and Broadhurst Method (KSB) pipeline verified against high-resolution Hubble Space Telescope imaging that covers part of the CFHTLS. Our i'-band measurements are also consistent with an analysis of independent r'-band imaging. The reconstructed lensing convergence map contains 301 peaks with signal-to-noise ratio ? > 3.5, consistent with predictions of a ?CDM model. Of these peaks, 126 lie within 3farcm0 of a brightest central galaxy identified from multicolor optical imaging in an independent, red sequence survey. We also identify seven counterparts for massive clusters previously seen in X-ray emission within 6 deg2 XMM-LSS survey. With photometric redshift estimates for the source galaxies, we use a tomographic lensing method to fit the redshift and mass of each convergence peak. Matching these to the optical observations, we confirm 85 groups/clusters with ?2 reduced < 3.0, at a mean redshift langzc rang = 0.36 and velocity dispersion lang? c rang = 658.8 km s-1. Future surveys, such as DES, LSST, KDUST, and EUCLID, will be able to apply these techniques to map clusters in much larger volumes and thus tightly constrain cosmological models.
Shan, HuanYuan; Kneib, Jean-Paul; Tao, Charling; Fan, Zuhui; Jauzac, Mathilde; Limousin, Marceau; Massey, Richard; Rhodes, Jason; Thanjavur, Karun; McCracken, Henry J.
OBSERVING GRAVITATIONAL LENSING EFFECTS BY Sgr A* WITH GRAVITY
The massive black hole Sgr A* at the Galactic center is surrounded by a cluster of stars orbiting around it. Light from these stars is bent by the gravitational field of the black hole, giving rise to several phenomena: astrometric displacement of the primary image, the creation of a secondary image that may shift the centroid of Sgr A*, and magnification effects on both images. The soon-to-be second-generation Very Large Telescope Interferometer instrument GRAVITY will perform observations in the near-infrared of the Galactic center at unprecedented resolution, opening the possibility of observing such effects. Here we investigate the observability limits for GRAVITY of gravitational lensing effects on the S-stars in the parameter space 1[D{sub LS}, {gamma}, K], where D{sub LS} is the distance between the lens and the source, {gamma} is the alignment angle of the source, and K is the source's apparent magnitude in the K band. The easiest effect to observe in future years is the astrometric displacement of primary images. In particular, the shift of the star S17 from its Keplerian orbit will be detected as soon as GRAVITY becomes operative. For exceptional configurations, it will be possible to detect effects related to the spin of the black hole or post-Newtonian orders in the deflection.
Bozza, V. [Department of Physics 'E.R. Caianiello', University of Salerno, Via Ponte Don Melillo, Fisciano I-84084 (Italy); Mancini, L., E-mail: firstname.lastname@example.com, E-mail: firstname.lastname@example.com [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany)
Cross-Correlation Tomography: Measuring Dark Energy Evolution with Weak Lensing
A cross-correlation technique of lensing tomography is developed to probe dark energy in the Universe. The variation of weak shear with redshift around foreground galaxies depends only on the angular distances and is robust to the dominant systematic error in lensing. We estimate the margin�alized accuracies that deep lensing surveys with photometric redshifts can provide on the dark energy density
Bhuvnesh Jain; Andy Taylor
The Optical Gravitational Lensing Experiment (OGLE): Bohdan's and Our Great Adventure
NASA Astrophysics Data System (ADS)
We present sixteen years of history of the Optical Gravitational Lensing Experiment. We also discuss the main discoveries of the OGLE project and its contributions to many fields of modern astrophysics.
Udalski, A.
Higher order statistics of weak lensing shear and flexion
NASA Astrophysics Data System (ADS)
Owing to their more extensive sky coverage and tighter control on systematic errors, future deep weak lensing surveys should provide a better statistical picture of the dark matter clustering beyond the level of the power spectrum. In this context, the study of non-Gaussianity induced by gravity can help tighten constraints on the background cosmology by breaking parameter degeneracies, as well as throwing light on the nature of dark matter, dark energy or alternative gravity theories. Analysis of the shear or flexion properties of such maps is more complicated than the simpler case of the convergence due to the spinorial nature of the fields involved. Here we develop analytical tools for the study of higher order statistics such as the bispectrum (or trispectrum) directly using such maps at different source redshift. The statistics we introduce can be constructed from cumulants of the shear or flexions, involving the cross-correlation of squared and cubic maps at different redshifts. Typically, the low signal-to-noise ratio prevents recovery of the bispectrum or trispectrum mode by mode. We define power spectra associated with each multispectrum which compress some of the available information of higher order multispectra. We show how these can be recovered from noisy observational data even in the presence of an arbitrary mask, which introduces mixing between electric (E-type) and magnetic (B-type) polarization, in an unbiased way. We also introduce higher order cross-correlators which can cross-correlate lensing shear with different tracers of large-scale structures.
Munshi, Dipak; Smidt, Joseph; Heavens, Alan; Coles, Peter; Cooray, Asantha
Scattering of weak gravitational waves by a sphere
By considering the gravitational field in the linearized Einstein theory, the scattering of a weak gravitational plane wave by a sphere is studied. The spherical components of the field and the differential scattering cross section are given in terms of the spin-weighted spherical harmonics and the effect on the polarization of the waves is analyzed.
G. F. Torres Del Castillo; L. C. Cortes Cuatli
Scattering of weak gravitational waves by a sphere.
NASA Astrophysics Data System (ADS)
By considering the gravitational field in the linearized Einstein theory, the scattering of a weak gravitational plane wave by a sphere is studied. The spherical components of the field and the differential scattering cross section are given in terms of the spin-weighted spherical harmonics and the effect on the polarization of the waves is analyzed.
Torres Del Castillo, G. F.; Cortes Cuatli, L. C.
Joint reconstruction of galaxy clusters from gravitational lensing and thermal gas. I. Outline of a non-parametric method
NASA Astrophysics Data System (ADS)
We present a method of estimating the lensing potential from massive galaxy clusters for given observational X-ray data. The concepts developed and applied in this work can be easily combined with other techniques to infer the lensing potential, e.g. weak gravitational lensing or galaxy kinematics, to obtain an overall best-fit model for the lensing potential. After elaborating on the physical details and assumptions the method is based on, we explain how the numerical algorithm itself is implemented with a Richardson-Lucy algorithm as a central part. Our reconstruction method is tested on simulated galaxy clusters with a spherically symmetric NFW density profile filled with gas in hydrostatic equilibrium. We describe in detail how these simulated observational data sets are created and how they need to be fed into our algorithm. We tested the robustness of the algorithm against small parameter changes and estimate the quality of the reconstructed lensing potentials. As it turns out, we achieve a very high degree of accuracy in reconstructing the lensing potential. The statistical errors remain below 2.0%, whereas the systematical error does not exceed 1.0%.
Konrad, S.; Majer, C. L.; Meyer, S.; Sarli, E.; Bartelmann, M.
Herschel-ATLAS/GAMA: SDSS cross-correlation induced by weak lensing
NASA Astrophysics Data System (ADS)
We report a highly significant (>10?) spatial correlation between galaxies with S350 ?m ? 30 mJy detected in the equatorial fields of the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) with estimated redshifts ? 1.5, and Sloan Digital Sky Survey (SDSS) or Galaxy And Mass Assembly (GAMA) galaxies at 0.2 ? z ? 0.6. The significance of the cross-correlation is much higher than those reported so far for samples with non-overlapping redshift distributions selected in other wavebands. Extensive, realistic simulations of clustered sub-mm galaxies amplified by foreground structures confirm that the cross-correlation can be explained by weak gravitational lensing (? < 2). The simulations also show that the measured amplitude and range of angular scales of the signal are larger than can be accounted for by galaxy-galaxy weak lensing. However, for scales ? 2 arcmin, the signal can be reproduced if SDSS/GAMA galaxies act as signposts of galaxy groups/clusters with halo masses in the range 1013.2-1014.5 M?. The signal detected on larger scales appears to reflect the clustering of such haloes.
Gonz�lez-Nuevo, J.; Lapi, A.; Negrello, M.; Danese, L.; De Zotti, G.; Amber, S.; Baes, M.; Bland-Hawthorn, J.; Bourne, N.; Brough, S.; Bussmann, R. S.; Cai, Z.-Y.; Cooray, A.; Driver, S. P.; Dunne, L.; Dye, S.; Eales, S.; Ibar, E.; Ivison, R.; Liske, J.; Loveday, J.; Maddox, S.; Micha?owski, M. J.; Robotham, A. S. G.; Scott, D.; Smith, M. W. L.; Valiante, E.; Xia, J.-Q.
An X-ray Study of Gravitational Lenses: Probing AGNs and the Cosmos with the Aid of Lensing
NASA Astrophysics Data System (ADS)
Gravitational lensing of distant quasars by intervening galaxies, where multiple images are formed, is a spectacular phenomenon in the universe. With the advent of Chandra, it is possible to resolve for the first time in the X-ray band lensed quasar images with separations greater than about 0.3 arcsec. We use lensing as a tool to study AGN and Cosmology. The X-ray band probes the inner most regions of the central engines of AGN. The lensing flux magnification, ranging from a few to 100, enables us to obtain high signal-to-noise spectra and light-curves of high redshift quasars with less observing time and allows us to search for changes in quasar spectroscopic properties and X-ray flux variability over three orders of magnitude in intrinsic X-ray luminosity. One surprising result that we found in the sample of radio-quiet, high-redshift lensed quasars is a possible ? -Lx relation, which may indicate that high redshift quasars are accreting close to their Eddington limits. We also use the microlensing effects induced by stars in the lensing galaxies to study the structure of the accretion discs of AGN, which cannot be resolved by current instruments. In the case of Q2237+0305, where an X-ray microlensing event was detected, we concluded that the broad Iron line region which is affected by the GR and SR effects is smaller than the X-ray continuum region. Finally we use gravitational lensing as a tool to study Cosmology. By measuring the time-delays between different lensed images it is possible to constrain the Hubble constant independently from other techniques. We have successfully measured time-delays in two lensed systems and have placed a lower limit in a third one. We gratefully acknowledge the financial support by NASA grant NAS 8-01128.
Dai, X.
Weak Lensing by Large-Scale Structure: A Dark Matter Halo Approach.
Weak gravitational lensing observations probe the spectrum and evolution of density fluctuations and the cosmological parameters that govern them, but they are currently limited to small fields and subject to selection biases. We show how the expected signal from large-scale structure arises from the contributions from and correlations between individual halos. We determine the convergence power spectrum as a function of the maximum halo mass and so provide the means to interpret results from surveys that lack high-mass halos either through selection criteria or small fields. Since shot noise from rare massive halos is mainly responsible for the sample variance below 10&arcmin;, our method should aid our ability to extract cosmological information from small fields. PMID:10828996
Cooray; Hu; Miralda-Escud�
New Developments on Inverse Polygon Mapping to Calculate Gravitational Lensing Magnification Maps: Optimized Computations
We derive an exact solution (in the form of a series expansion) to compute gravitational lensing magnification maps. It is based on the backward gravitational lens mapping of a partition of the image plane in polygonal cells (inverse polygon mapping, IPM), not including critical points (except perhaps at the cell boundaries). The zeroth-order term of the series expansion leads to
E. Mediavilla; T. Mediavilla; J. A. Mu�oz; O. Ariza; P. Lopez; C. Gonzalez-Morcillo; J. Jimenez-Vicente
Gravitational anomaly and Hawking radiation near a weakly isolated horizon
Based on the idea of the work by Wilczek and his collaborators, we consider the gravitational anomaly near a weakly isolated horizon. We find that there exists a universal choice of tortoise coordinate for any weakly isolated horizon. Under this coordinate, the leading behavior of a quite arbitrary scalar field near a horizon is a 2-dimensional chiral scalar field. This
Wu Xiaoning; Huang Chaoguang; Sun Jiarui
The impact of high spatial frequency atmospheric distortions on weak-lensing measurements
NASA Astrophysics Data System (ADS)
High-precision cosmology with weak gravitational lensing requires a precise measure of the point spread function across the imaging data where the accuracy to which high spatial frequency variation can be modelled is limited by the stellar number density across the field. We analyse dense stellar fields imaged at the Canada-France-Hawaii Telescope to quantify the degree of high spatial frequency variation in ground-based imaging point spread functions and compare our results to models of atmospheric turbulence. The data show an anisotropic turbulence pattern with an orientation independent of the wind direction and wind speed. We find the amplitude of the high spatial frequencies to decrease with increasing exposure time as t-1/2, and find a negligibly small atmospheric contribution to the point spread function ellipticity variation for exposure times t > 180 s. For future surveys analysing shorter exposure data, this anisotropic turbulence will need to be taken into account as the amplitude of the correlated atmospheric distortions becomes comparable to a cosmological lensing signal on scales less than �10 arcmin. This effect could be mitigated, however, by correlating galaxy shear measured on exposures imaged with a time separation greater than 50 s, for which we find the spatial turbulence patterns to be uncorrelated.
Heymans, Catherine; Rowe, Barnaby; Hoekstra, Henk; Miller, Lance; Erben, Thomas; Kitching, Thomas; van Waerbeke, Ludovic
The effect of satellite galaxies on gravitational lensing flux ratios
NASA Astrophysics Data System (ADS)
Gravitational lenses with anomalous flux ratios are often cited as possible evidence for dark matter satellites predicted by simulations of hierarchical merging in cold dark matter cosmogonies. We show that the fraction of quads with anomalous flux ratios depends primarily on the total mass and spatial extent of the satellites, and the characteristic length-scale d1/2 of their distribution. If d1/2 ~ 100kpc, then for a moderately elliptical galaxy with a line-of-sight velocity dispersion of ~ 250kms-1, a mass of ~3 � 109Msolar in highly concentrated (Plummer model) satellites is needed for 20 per cent of quadruplets to show anomalous flux ratios, rising to ~1.25 � 1010Msolar for 50 per cent. Several times these masses are required if the satellites have more extended Hernquist profiles. Compared to a typical elliptical, the flux ratios of quads formed by typical edge-on disc galaxies with maximum discs are significantly less susceptible to changes through substructure - three times the mass in satellite galaxies is needed to affect 50 per cent of the systems. In many of the lens systems with anomalous flux ratios, there is evidence for visible satellites (e.g. B2045+265 or MG0414+0534). We show that if the anomaly is produced by substructure with properties similar to the simulations, then optically identified substructure should not be preponderant among lens systems with anomalies. There seem to be two possible resolutions of this difficulty. First, in some cases, visible substructure may be projected within or close to the Einstein radius and wrongly ascribed as the culprit, whereas dark matter substructure is causing the flux anomaly. Secondly, bright satellites, in which baryon cooling and condensation have taken place, may have higher central densities than dark satellites, rendering them more efficient at causing flux anomalies.
Shin, E. M.; Evans, N. W.
Intrinsic galaxy shapes and alignments - II. Modelling the intrinsic alignment contamination of weak lensing surveys
NASA Astrophysics Data System (ADS)
Intrinsic galaxy alignments constitute the major astrophysical systematic of forthcoming weak gravitational lensing surveys but also yield unique insights into galaxy formation and evolution. We build analytic models for the distribution of galaxy shapes based on halo properties extracted from the Millennium Simulation, differentiating between early- and late-type galaxies as well as central galaxies and satellites. The resulting ellipticity correlations are investigated for their physical properties and compared to a suite of current observations. The best-faring model is then used to predict the intrinsic alignment contamination of planned weak lensing surveys. We find that late-type galaxy models generally have weak intrinsic ellipticity correlations, marginally increasing towards smaller galaxy separation and higher redshift. The signal for early-type models at fixed halo mass strongly increases by three orders of magnitude over two decades in galaxy separation, and by one order of magnitude from z = 0 to z = 2. The intrinsic alignment strength also depends strongly on halo mass, but not on galaxy luminosity at fixed mass, or galaxy number density in the environment. We identify models that are in good agreement with all observational data, except that all models overpredict alignments of faint early-type galaxies. The best model yields an intrinsic alignment contamination of a Euclid-like survey between 0.5 and 10 per cent at z > 0.6 and on angular scales larger than a few arcminutes. Cutting 20 per cent of red foreground galaxies using observer-frame colours can suppress this contamination by up to a factor of 2.
Joachimi, B.; Semboloni, E.; Hilbert, S.; Bett, P. E.; Hartlap, J.; Hoekstra, H.; Schneider, P.
Fingerprinting dark energy. II. Weak lensing and galaxy clustering tests
The characterization of dark energy is a central task of cosmology. To go beyond a cosmological constant, we need to introduce at least an equation of state and a sound speed and consider observational tests that involve perturbations. If dark energy is not completely homogeneous on observable scales, then the Poisson equation is modified and dark matter clustering is directly affected. One can then search for observational effects of dark energy clustering using dark matter as a probe. In this paper we exploit an analytical approximate solution of the perturbation equations in a general dark energy cosmology to analyze the performance of next-decade large-scale surveys in constraining equation of state and sound speed. We find that tomographic weak lensing and galaxy redshift surveys can constrain the sound speed of the dark energy only if the latter is small, of the order of c{sub s} < or approx. 0.01 (in units of c). For larger sound speeds the error grows to 100% and more. We conclude that large-scale structure observations contain very little information about the perturbations in canonical scalar field models with a sound speed of unity. Nevertheless, they are able to detect the presence of cold dark energy, i.e. a dark energy with nonrelativistic speed of sound.
Sapone, Domenico [Departamento de Fisica Teorica and Instituto de Fisica Teorica, Universidad Autonoma de Madrid IFT-UAM/CSIC, Cantoblanco, Madrid (Spain); Kunz, Martin [Departement de Physique Theorique, Universite de Geneve, 24 quai Ernest Ansermet, CH-1211 Geneve 4 (Switzerland); Institut d'Astrophysique Spatiale, Universite Paris-Sud XI, Orsay 91405 (France); Astronomy Centre, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Amendola, Luca [University of Heidelberg, Philosophenweg 16, 69120 Heidelberg (Germany); INAF/Rome (Italy)
Weak-lensing mass estimates of galaxy groups and the line-of-sight contamination
NASA Astrophysics Data System (ADS)
Weak lensing is an important technique to determine the masses of galaxy groups. However, the distortion imprint on the shape of the background galaxies is not only affected by the gravitational field of the main group, but also affected by all the mass content along the line of sight. Using COSMOS shear mock data, we study the shear profile around 165 groups and investigate the level at which the neighbouring groups can enhance or suppress the shear signal from the main halo. The mock data are based on Canada-France-Hawaii Telescope and Subaru observations, which are used to obtain the photometric redshifts of galaxies in the field and a realistic galaxy density, given by the weak-lensing distortion analysis of the observed data. We further use information on the galaxy groups (having a median mass and redshift of M200= 3.1 � 1013 M? and z = 0.68, respectively) from the COSMOS X-ray catalogue of extended sources. The expected gravitational shear field of these groups is calculated assuming that the haloes are described by Navarro-Frenk-White density profiles, and the total shear is computed by summing the shear over all the lenses. We conclude that, on average, the signal-to-noise ratio for a detection of the main halo is affected by ? with respect to the signal-to-noise ratio the same halo would have if it was isolated in the sky. Groups with neighbours that are close in projected distance (?1 arcmin) are the most affected, but haloes located at larger angular distances also cause a measurable shear signal. These (angular) distant groups can be interpreted as uncorrelated large-scale structure. The average bias in the mass-excess estimate of individual groups that is introduced by the external haloes is zero with an rms of �6-72 per cent, depending on the aperture size used. One way to eliminate this bias is by stacking the density profile of several groups. The shear signal introduced by large-scale structure acts as an external source of noise. The averaged uncertainty introduced is ? per component for an aperture size of ?� 5 arcmin, which corresponds to �1.8 per cent of the one-component intrinsic ellipticity value. This large-scale structure noise error becomes equal to intrinsic ellipticity noise if there are measurements for �3000 galaxies within a certain aperture, a number that is already achieved by current deep surveys such as COSMOS and therefore that should not be ignored.
Spinelli, P. F.; Seitz, S.; Lerchster, M.; Brimioulle, F.; Finoguenov, A.
IM3SHAPE: a maximum likelihood galaxy shear measurement code for cosmic gravitational lensing
NASA Astrophysics Data System (ADS)
We present and describe IM3SHAPE, a new publicly available galaxy shape measurement code for weak gravitational lensing shear. IM3SHAPE performs a maximum likelihood fit of a bulge-plus-disc galaxy model to noisy images, incorporating an applied point spread function. We detail challenges faced and choices made in its design and implementation, and then discuss various limitations that affect this and other maximum likelihood methods. We assess the bias arising from fitting an incorrect galaxy model using simple noise-free images and find that it should not be a concern for current cosmic shear surveys. We test IM3SHAPE on the Gravitational Lensing Accuracy Testing 2008 (GREAT08) challenge image simulations, and meet the requirements for upcoming cosmic shear surveys in the case that the simulations are encompassed by the fitted model, using a simple correction for image noise bias. For the fiducial branch of GREAT08 we obtain a negligible additive shear bias and sub-two per cent level multiplicative bias, which is suitable for analysis of current surveys. We fall short of the sub-per cent level requirement for upcoming surveys, which we attribute to a combination of noise bias and the mismatch between our galaxy model and the model used in the GREAT08 simulations. We meet the requirements for current surveys across all branches of GREAT08, except those with small or high noise galaxies, which we would cut from our analysis. Using the GREAT08 metric we we obtain a score of Q = 717 for the usable branches, relative to the goal of Q = 1000 for future experiments. The code is freely available from https://bitbucket.org/joezuntz/im3shape
Zuntz, Joe; Kacprzak, Tomasz; Voigt, Lisa; Hirsch, Michael; Rowe, Barnaby; Bridle, Sarah
We study the bias and scatter in mass measurements of galaxy clusters resulting from fitting a spherically symmetric Navarro, Frenk, and White model to the reduced tangential shear profile measured in weak-lensing (WL) observations. The reduced shear profiles are generated for {approx}10{sup 4} cluster-sized halos formed in a {Lambda}CDM cosmological N-body simulation of a 1 h{sup -1} Gpc box. In agreement with previous studies, we find that the scatter in the WL masses derived using this fitting method has irreducible contributions from the triaxial shapes of cluster-sized halos and uncorrelated large-scale matter projections along the line of sight. Additionally, we find that correlated large-scale structure within several virial radii of clusters contributes a smaller, but nevertheless significant, amount to the scatter. The intrinsic scatter due to these physical sources is {approx}20% for massive clusters and can be as high as {approx}30% for group-sized systems. For current, ground-based observations, however, the total scatter should be dominated by shape noise from the background galaxies used to measure the shear. Importantly, we find that WL mass measurements can have a small, {approx}5%-10%, but non-negligible amount of bias. Given that WL measurements of cluster masses are a powerful way to calibrate cluster mass-observable relations for precision cosmological constraints, we strongly emphasize that a robust calibration of the bias requires detailed simulations that include more observational effects than we consider here. Such a calibration exercise needs to be carried out for each specific WL mass estimation method, as the details of the method determine in part the expected scatter and bias. We present an iterative method for estimating mass M{sub 500c} that can eliminate the bias for analyses of ground-based data.
Becker, Matthew R. [Department of Physics, 5720 S. Ellis Avenue, University of Chicago, Chicago, IL 60637 (United States); Kravtsov, Andrey V. [Kavli Institute for Cosmological Physics, 5640 South Ellis Avenue, University of Chicago, Chicago, IL 60637 (United States)
SDSS J0246-0825: A New Gravitationally Lensed Quasar from the Sloan Digital Sky Survey
We report the discovery of a new two-image gravitationally lensed quasar, SDSS J024634.11-082536.2 (SDSS J0246-0825). This object was selected as a lensed quasar candidate from the Sloan Digital Sky Survey (SDSS) by the same algorithm that was used to discover other SDSS lensed quasars (e.g., SDSS J0924+0219). Multicolor imaging with the Magellan Consortium's Walter Baade 6.5-m telescope and the spectroscopic observations using the W. M. Keck Observatory's Keck II telescope confirm that SDSS J0246-0825 consists of two lensed images ({Delta}{theta} = 1''.04) of a source quasar at z = 1.68. Imaging observations with the Keck telescope and the Hubble Space Telescope reveal an extended object between the two quasar components, which is likely to be a lensing galaxy of this system. From the absorption lines in the spectra of quasar components and the apparent magnitude of the galaxy, combined with the expected absolute magnitude from the Faber-Jackson relation, we estimate the redshift of the lensing galaxy to be z = 0.724. A highly distorted ring is visible in the Hubble Space Telescope images, which is likely to be the lensed host galaxy of the source quasar. Simple mass modeling predicts the possibility that there is a small (faint) lensing object near the primary lensing galaxy.
Inada, N; Burles, S; Gregg, M D; Becker, R H; Schechter, P L; Eisenstein, D J; Oguri, M; Castander, F J; Hall, P B; Johnston, D E; Pindor, B; Richards, G T; Schneider, D P; White, R L; Brinkmann, J; Szalay, A; York, D G
Measuring gravitational lensing of the cosmic microwave background using cross correlation with large scale structure
NASA Astrophysics Data System (ADS)
We cross correlate the gravitational lensing map extracted from cosmic microwave background measurements by the Wilkinson Microwave Anisotropy Probe with the radio galaxy distribution from the NRAO VLA Sky Survey (NVSS) by using a quadratic estimator technique. We use the full covariance matrix to filter the data, and calculate the cross-power spectra for the lensing-galaxy correlation. We explore the impact of changing the values of cosmological parameters on the lensing reconstruction, and obtain statistical detection significances at >3?. The results of all cross correlations pass the curl null test as well as a complementary diagnostic test using the NVSS data in equatorial coordinates. We forecast the potential for Planck and NVSS to constrain the lensing-galaxy cross correlation as well as the galaxy bias. The lensing-galaxy cross-power spectra are found to be Gaussian distributed.
Feng, Chang; Aslanyan, Grigor; Manohar, Aneesh V.; Keating, Brian; Paar, Hans P.; Zahn, Oliver
SDSS J094604.90+183541.8: A GRAVITATIONALLY LENSED QUASAR AT z = 4.8
We report the discovery of a gravitationally lensed quasar identified serendipitously in the Sloan Digital Sky Survey (SDSS). The object, SDSS J094604.90+183541.8, was initially targeted for spectroscopy as a luminous red galaxy, but the SDSS spectrum has the features of both a z = 0.388 galaxy and a z = 4.8 quasar. We have obtained additional imaging that resolves the system into two quasar images separated by 3.''06 and a bright galaxy that is strongly blended with one of the quasar images. We confirm spectroscopically that the two quasar images represent a single-lensed source at z = 4.8 with a total magnification of 3.2, and we derive a model for the lensing galaxy. This is the highest redshift lensed quasar currently known. We examine the issues surrounding the selection of such an unusual object from existing data and briefly discuss implications for lensed quasar surveys.
McGreer, Ian D.; Fan Xiaohui; Bian Fuyan; Farnsworth, Kara [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065 (United States); Hall, Patrick B. [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, ON, M3J 1P3 (Canada); Inada, Naohisa [Cosmic Radiation Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan); Oguri, Masamune [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Strauss, Michael A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States)
Designing Future Dark Energy Space Missions: II. Photometric Redshift of Space Weak Lensing Optimized Survey
Accurate weak-lensing analysis requires not only accurate measurement of\\u000agalaxy shapes but also precise and unbiased measurement of galaxy redshifts.\\u000aThe photometric redshift technique appears as the only possibility to determine\\u000athe redshift of the background galaxies used in the weak-lensing analysis.\\u000aUsing the photometric redshift quality, simple shape measurement requirements,\\u000aand a proper sky model, we explore what could
S. Jouvel; J. P. Kneib; G. Bernstein; O. Ilbert; P. Jelinsky; B. Milliard; A. Ealet; C. Schimd; T. Dahlen; S. Arnouts
Cusped mass density profiles and magnification ratios of double-image gravitational lenses
NASA Astrophysics Data System (ADS)
We have been able to connect statistics of the observed double-image gravitational lenses to general properties of the internal structure of lens haloes. Our analytical theory for the generalization of the Navarro, Frenk & White (NFW) profile (GNFW) lenses with a parametrized cusp slope (?) gives a relation connecting the cusp slope of a lens mass profile to the observed magnification ratio of the produced images and location of the optical axis. The relation does not depend on the cosmology, total lens mass, concentration or redshifts of the the lens and the lensed object. Simple geometry of axially-symmetric lensing and the aforementioned relation enables us to define the cusp slope limit value, ?CSL, for the cusp slope, independent of the location of the optical axis. The threshold cusp slope value ?=?CSL is the shallowest slope for the inner part of the GNFW profile that can produce the observed magnification ratio with any lensing configuration. We use a distribution of these threshold values that depend only on the observed flux ratio of the lensed images, in a statistical study of the double image lenses in order to limit the possible cusp slope values and identify whether there exists a population of haloes with similar profiles. Our theoretical fit indicates that within our sample of double-image gravitational lenses, most of the haloes have the cusp slope ?=-1.95 � 0.02. We have also found an indication of a second population of lenses with a cusp slope value ?=-1.51 � 0.02. We estimate that there is about 97 per cent probability that the observed feature in the threshold value limit distribution is produced by a second population of lenses, with their own characteristic density profile. The data indicating the exact characteristics of the subpopulation are noisy. Roughly one out of eight haloes within the sample belongs to this shallower cusp slope group. We investigate the accuracy of our analysis by constructing mock catalogues with Monte Carlo method.
Mutka, P. T.
Parametric strong gravitational lensing analysis of Abell 1689
NASA Astrophysics Data System (ADS)
We have derived the mass distribution of galaxy cluster Abell 1689 within 0.3h-170Mpc of the cluster centre using its strong lensing (SL) effect on 32 background galaxies, which are mapped in altogether 107 multiple images. The multiple images are based on some from the literature with modifications to both include new and exclude some of the original image systems. The cluster profile is explored further out to ~2.5h-170Mpc with weak lensing (WL) shear measurements from the literature. The masses of ~200 cluster galaxies are measured with the Fundamental Plane (FP) in order to model accurately the small-scale mass structure in the cluster. The cluster galaxies are modelled as elliptical truncated isothermal spheres. The scalings of the truncation radii with the velocity dispersions of galaxies are assumed to match those of: (i) field galaxies; and (ii) theoretical expectations for galaxies in dense environments. The dark matter (DM) component of the cluster is described by either non-singular isothermal ellipsoids (NSIE) or elliptical versions of the universal DM profile (elliptical Navarro, Frenk & White, ENFW). To account for substructure in the DM we allow for two DM haloes. The fitting of a non-singular isothermal sphere (NSIS) to the smooth DM component results in a velocity dispersion of 1450+39-31kms-1 and a core radius of 77+10-8h-170kpc, while a Navarro, Frenk & White (NFW) profile has an r200 of 2.86 +/- 0.16h-170Mpc (M200 = 3.2 � 1015Msolarh70) and a concentration of 4.7+0.6-0.5. The total mass profile is well described by either a NSIS profile with ? = 1514+18-17kms-1 and a core radius of rc = 71 +/- 5h-170kpc, or an NFW profile with C = 6.0 +/- 0.5 and r200 = 2.82 +/- 0.11h-170Mpc (M200 = 3.0 � 1015Msolarh70). The errors are assumed to be due to the error in assigning masses to the individual galaxies in the galaxy component. Their small size is due to the very strong constraints imposed by multiple images and the ability of the smooth DM component to adjust to uncertainties in the galaxy masses. The agreement in the total mass profile between this work and that of the literature is better than 1? at all radii, despite the considerable differences in the methodology used. Using the same image configuration as used in the literature, we obtain a SL model that is superior to some in the literature (rms of 2.7 compared to 3.2arcsec). This is very surprising considering the larger freedom in the surface mass profile in their grid modelling. The difference is most likely a result of the careful inclusion of the cluster galaxies. Using also WL shear measurements from the literature, we can constrain the profile further out to r ~ 2.5h-170Mpc. The best-fitting parameters change to ? = 1499 +/- 15kms-1 and rc = 66 +/- 5h-170kpc for the NSIS profile and C = 7.6 +/- 0.5 and r200 = 2.55 +/- 0.07h-170Mpc (M200 = 2.3 � 1015Msolarh70) for the NFW profile.
Halkola, A.; Seitz, S.; Pannella, M.
Reducing distance errors for standard candles and standard sirens with weak-lensing shear and flexion maps
NASA Astrophysics Data System (ADS)
Gravitational lensing induces significant errors in the measured distances to high-redshift standard candles and standard sirens such as Type Ia supernovae, gamma-ray bursts and merging supermassive black hole binaries. There will therefore be a significant benefit from correcting for the lensing error by using independent and accurate estimates of the lensing magnification. Here, we investigate how accurately the magnification can be inferred from convergence maps reconstructed from galaxy shear and flexion data. We employ ray-tracing through the Millennium Simulation (MS) to simulate lensing observations in large fields, and perform a weak-lensing reconstruction on the simulated fields. We identify optimal ways to filter the reconstructed convergence maps and to convert them to magnification maps, and analyse the resulting relation between the estimated and true magnification for sources at redshifts zS= 1 to 5. We find that a deep shear survey with 100 galaxies arcmin-2 can help to reduce the lensing-induced distance errors for standard candles/sirens at redshifts zS? 1.5 (zS? 5) on average by 20 per cent (10 per cent), whereas a futuristic survey with shear and flexion estimates from 500 galaxies arcmin-2 yields much larger reductions of 50 per cent (35 per cent). For redshifts zS? 3, a further improvement by �5 per cent can be achieved, if the individual redshifts of the galaxies are used in the reconstruction. Moreover, the reconstruction allows one to identify regions for which the convergence is low, and in which an error reduction by up to 75 per cent can be achieved. Such strongly reduced magnification uncertainties will greatly improve the value of high-redshift standard candles/sirens as cosmological probes.
Hilbert, Stefan; Gair, Jonathan R.; King, Lindsay J.
Weak lensing reconstruction through cosmic magnification - I. A minimal variance map reconstruction
NASA Astrophysics Data System (ADS)
We present a concept study on weak lensing map reconstruction through the cosmic magnification effect in galaxy number density distribution. We propose a minimal variance linear estimator to minimize both the dominant systematic and statistical errors in the map reconstruction. It utilizes the distinctively different flux dependences to separate the cosmic magnification signal from the overwhelming galaxy intrinsic clustering noise. It also minimizes the shot noise error by an optimal weighting scheme on the galaxy number density in each flux bin. Our method is in principle applicable to all galaxy surveys with reasonable redshift information. We demonstrate its applicability against the planned Square Kilometer Array survey, under simplified conditions. Weak lensing maps reconstructed through our method are complementary to that from cosmic shear and cosmic microwave background (CMB) and 21-cm lensing. They are useful for cross-checking over systematic errors in weak lensing reconstruction and for improving cosmological constraints.
Yang, Xinjuan; Zhang, Pengjie
Effects of Multiple Weak Deflections on the Galaxy-Galaxy Lensing Signal
NASA Astrophysics Data System (ADS)
Galaxy-galaxy lensing is a powerful tool with which the dark mass distribution around galaxies can be constrained directly. One potential complication to the interpretation of an observed galaxy-galaxy lensing signal, however, is the effect of multiple weak deflections. A number of previous studies have shown that for a typical deep data set, background source galaxies will have been lensed at a comparable level by two or more foreground galaxies. Contrary to naive expectations, these multiple weak deflections that are undergone by the images of the source galaxies do not generally cancel out, nor can they usually be ignored. Previous work as shown that at large angular scales the net shear experienced by distant source galaxies due to all foreground lenses generally exceeds the shear due to the single lens with the smallest impact parameter (the "closest lens"). When multiple deflections that have occurred in the observational data are not included in the interpretation of the observed shear profile, systematic errors in the constraints on the lens masses can occur. Here we explore the effects of multiple deflections on the galaxy-galaxy lensing signal using various toy models. We show that the main cause for the difference between the shear profile resulting from all foreground weak lenses and the shear profile resulting from the single closest weak lens is the fact that galaxies have a broad distribution in redshift space. That is, it is not correct to consider realistic galaxy-galaxy lensing as being confined primarily to a single lens plane in redshift space. We also explore the effect of multiple weak deflections on the surface mass density inferred for foreground lenses when the net mean tangential shear (i.e., the shear that results when all multiple weak deflections are taken into account) is used.
Brainerd, Tereasa G.; Blumenthal, Kelly
The effective number density of galaxies for weak lensing measurements in the LSST project
NASA Astrophysics Data System (ADS)
Future weak lensing surveys potentially hold the highest statistical power for constraining cosmological parameters compared to other cosmological probes. The statistical power of a weak lensing survey is determined by the sky coverage, the inverse of the noise in shear measurements and the galaxy number density. The combination of the latter two factors is often expressed in terms of neff - the `effective number density of galaxies used for weak lensing measurements'. In this work, we estimate neff for the Large Synoptic Survey Telescope (LSST) project, the most powerful ground-based lensing survey planned for the next two decades. We investigate how the following factors affect the resulting neff of the survey with detailed simulations: (1) survey time, (2) shear measurement algorithm, (3) algorithm for combining multiple exposures, (4) inclusion of data from multiple filter bands, (5) redshift distribution of the galaxies and (6) masking and blending. For the first time, we quantify in a general weak lensing analysis pipeline the sensitivity of neff to the above factors. We find that with current weak lensing algorithms, expected distributions of observing parameters, and all lensing data (r and i band, covering 18 000 degree2 of sky) for LSST, neff ? 37 arcmin-2 before considering blending and masking, neff ? 31 arcmin-2 when rejecting seriously blended galaxies and neff ? 26 arcmin-2 when considering an additional 15 per cent loss of galaxies due to masking. With future improvements in weak lensing algorithms, these values could be expected to increase by up to 20 per cent. Throughout the paper, we also stress the ways in which neff depends on our ability to understand and control systematic effects in the measurements.
Chang, C.; Jarvis, M.; Jain, B.; Kahn, S. M.; Kirkby, D.; Connolly, A.; Krughoff, S.; Peng, E.-H.; Peterson, J. R.
The Optical Gravitational Lensing Experiment. Small Amplitude Variable Red Giants in the Magellanic Clouds
We present analysis of the large sample of variable red giants from the Large and Small Magellanic Clouds detected during the second phase of the Optical Gravitational Lensing Experiment (OGLE-II) and supplemented with OGLE-III photometry. Comparing pulsation properties of detected objects we find that they constitute two groups with clearly distinct features. In this paper we analyze in detail small
I. Soszynski; A. Udalski; M. Kubiak; M. Szymanski; G. Pietrzynski; K. Zebrun; O. Szewczyk; L. Wyrzykowski
Pc Imaging of Gravitational Lenses, WFPC Augmentation, Carryover
NASA Astrophysics Data System (ADS)
We propose to obtain imaging of four more recently discovered lenses: 1042+178, 1120+019, 1413+117, and 2118+132. Ground-based observations suggest that the angular resolution of HST will provide critical data. The aim is to obtain data which will help in the complete characterization of the lens systems. Observations will be made in the WFC and PC, using filters 555W and 814W, the former to emphasize the quasar images and the latter the lensing galaxies.
Westphal, J.
Gravitational lensing in WDM cosmologies: the cross-section for giant arcs
NASA Astrophysics Data System (ADS)
The nature of the dark sector of the Universe remains one of the outstanding problems in modern cosmology, with the search for new observational probes guiding the development of the next generation of observational facilities. Clues come from tension between the predictions from ? cold dark matter (?CDM) and observations of gravitationally lensed galaxies. Previous studies showed that galaxy clusters in the ?CDM are not strong enough to reproduce the observed number of lensed arcs. This work aims to constrain the warm dark matter (WDM) cosmologies by means of the lensing efficiency of galaxy clusters drawn from these alternative models. The lensing characteristics of two samples of simulated clusters in the ? warm dark matter and ?CDM cosmologies have been studied. The results show that even though the cold dark matter (CDM) clusters are more centrally concentrated and contain more substructures, the WDM clusters have slightly higher lensing efficiency than their CDM counterparts. The key difference is that WDM clusters have more extended and more massive subhaloes than CDM analogues. These massive substructures significantly stretch the critical lines and caustics and hence they boost the lensing efficiency of the host halo. Despite the increase in the lensing efficiency due to the contribution of massive substructures in the WDM clusters, this is not enough to resolve the arc statistics problem.
Mahdi, Hareth S.; van Beek, Martijn; Elahi, Pascal J.; Lewis, Geraint F.; Power, Chris; Killedar, Madhura
We explore the utility of Karhunen-Loeve (KL) analysis in solving practical problems in the analysis of gravitational shear surveys. Shear catalogs from large-field weak-lensing surveys will be subject to many systematic limitations, notably incomplete coverage and pixel-level masking due to foreground sources. We develop a method to use two-dimensional KL eigenmodes of shear to interpolate noisy shear measurements across masked regions. We explore the results of this method with simulated shear catalogs, using statistics of high-convergence regions in the resulting map. We find that the KL procedure not only minimizes the bias due to masked regions in the field, it also reduces spurious peak counts from shape noise by a factor of {approx}3 in the cosmologically sensitive regime. This indicates that KL reconstructions of masked shear are not only useful for creating robust convergence maps from masked shear catalogs, but also offer promise of improved parameter constraints within studies of shear peak statistics.
VanderPlas, J. T.; Connolly, A. J. [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Jain, B.; Jarvis, M. [Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6396 (United States)
Testing metallicity indicators at z � 1.4 with the gravitationally lensed galaxy CASSOWARY 20
NASA Astrophysics Data System (ADS)
We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR � 6 M? yr-1) galaxy at z = 1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy at z = 0.741. We analysed the integrated physical properties of the H II regions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be �1/7 of solar, while carbon is �50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid time-scale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from H II regions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of �2 uncertainty of each method. The interstellar medium (ISM) of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the ISM with speeds of up 750 km s-1, similar to the values measured in other high-z galaxies sustaining much higher rates of star formation.
James, Bethan L.; Pettini, Max; Christensen, Lise; Auger, Matthew W.; Becker, George D.; King, Lindsay J.; Quider, Anna M.; Shapley, Alice E.; Steidel, Charles C.
Cross-correlating Sunyaev-Zel'dovich and weak lensing maps
NASA Astrophysics Data System (ADS)
We present novel statistical tools to cross-correlate frequency cleaned thermal Sunyaev-Zel'dovich (tSZ) maps and tomographic weak lensing (wl) convergence maps. Moving beyond the lowest order cross-correlation, we introduce a hierarchy of mixed higher order statistics, the cumulants and cumulant correlators, to analyse non-Gaussianity in real space, as well as corresponding polyspectra in the harmonic domain. Using these moments, we derive analytical expressions for the joint two-point probability distribution function for smoothed tSZ (y) and convergence (?) maps. The presence of tomographic information allows us to study the evolution of higher order mixed tSZ-wl statistics with redshift. We express the joint PDFs p?y(?, y) in terms of individual one-point PDFs [p?(?), py(y)] and the relevant bias functions [b?(?), by(y)]. Analytical results for two different regimes are presented that correspond to the small and large angular smoothing scales. Results are also obtained for corresponding hotspots in the tSZ and convergence maps. In addition to results based on hierarchical techniques and perturbative methods, we present results of calculations based on the lognormal approximation. The analytical expressions derived here are generic and applicable to cross-correlation studies of arbitrary tracers of large-scale structure including, e.g., that of tSZ and soft X-ray background. We provide detailed comparison of our analytical results against state of the art Millennium Gas Simulations with and without non-gravitational effects such as pre-heating and cooling. Comparison of these results with gravity only simulations, shows reasonable agreement and can be used to isolate effect of non-gravitational physics from observational data.
Munshi, Dipak; Joudaki, Shahab; Coles, Peter; Smidt, Joseph; Kay, Scott T.
Gravitational lensing by the Sun of non-relativistic penetrating particles
NASA Astrophysics Data System (ADS)
The flux of weakly interacting particles from celestial sources, moving with a velocity v?0.2 c, can be temporarily amplified at the site of the Earth, due to gravitational lensing effects by the Sun. The effective amplification factor can be as much as �10 3 to �10 4, for a velocity bin-width of �0.1%. The theoretically motivated solar Kaluza-Klein axions provide a generic example of particles with a wide velocity spectrum, filling the gap between v? c (e.g. neutrinos) and v?10 -3c (e.g. dark matter (DM) candidates). If the putative particles come from a direction along the projected path of the Sun in the Sky, within a strip of �0.1� along the ecliptic, then, time windows of possible enhanced flows can be predicted. This suggestion can be implemented in the (re)-analysis of data from DM-experiments, and, it does not need any major experimental modification. In particular, performing a cross-correlation of data taken over a period more than 1 year, from the same or even also from other experiments, this can result to (un)predictable time windows of interest. Because, if burst-like events re-appear in following years in fixed dates, this will be an unambiguous identification of the cosmic origin of underground events, which were ignored before. Thus, thanks to solar gravitational effects, DM-experiments can be transformed to telescopes of penetrating non-relativistic particles with a field-of-view of �0.1�, or even more, along the ecliptic. The missing access to DM-data does not allow us to test this technique. We therefore suggest to the astroparticle physics community to release its data.
Hoffmann, D. H. H.; Jacoby, J.; Zioutas, K.
The Einstein Cross: Constraint on Dark Matter from Stellar Dynamics and Gravitational Lensing
NASA Astrophysics Data System (ADS)
We present two-dimensional line-of-sight stellar kinematics of the lens galaxy in the Einstein Cross, obtained with the GEMINI 8 m telescope, using the GMOS integral-field spectrograph. The stellar kinematics extend to a radius of 4'' (with 0farcs2 spaxels), covering about two-thirds of the effective (or half-light) radius Re ~= 6'' of this early-type spiral galaxy at redshift zl ~= 0.04, of which the bulge is lensing a background quasar at redshift zs ~= 1.7. The velocity map shows regular rotation up to ~100 km s-1 around the minor axis of the bulge, consistent with axisymmetry. The velocity dispersion map shows a weak gradient increasing toward a central (R < 1'') value of ?0 = 170 � 9 km s-1. We deproject the observed surface brightness from Hubble Space Telescope imaging to obtain a realistic luminosity density of the lens galaxy, which in turn is used to build axisymmetric dynamical models that fit the observed kinematic maps. We also construct a gravitational lens model that accurately fits the positions and relative fluxes of the four quasar images. We combine these independent constraints from stellar dynamics and gravitational lensing to study the total mass distribution in the inner parts of the lens galaxy. We find that the resulting luminous and total mass distribution are nearly identical around the Einstein radius RE = 0farcs89, with a slope that is close to isothermal, but which becomes shallower toward the center if indeed mass follows light. The dynamical model fits to the observed kinematic maps result in a total mass-to-light ratio Upsilondyn = 3.7 � 0.5 Upsilonsun,I (in the I band). This is consistent with the Einstein mass ME = 1.54 � 1010 M sun divided by the (projected) luminosity within RE , which yields a total mass-to-light ratio of Upsilon E = 3.4 Upsilonsun,I , with an error of at most a few percent. We estimate from stellar population model fits to colors of the lens galaxy a stellar mass-to-light ratio Upsilonsstarf from 2.8 to 4.1 Upsilonsun,I . Although a constant dark matter fraction of 20% is not excluded, dark matter may play no significant role in the bulge of this ~L sstarf early-type spiral galaxy.
van de Ven, Glenn; Falc�n-Barroso, Jes�s; McDermid, Richard M.; Cappellari, Michele; Miller, Bryan W.; de Zeeuw, P. Tim
Weak- and strong-lensing analyses of the triaxial matter distribution of Abell 1689
NASA Astrophysics Data System (ADS)
Haloes formed in the standard ? cold dark matter framework should follow a universal mass density profile and fit a well-defined mass-concentration relation. Lensing analyses of clusters with a large Einstein radius seem to contradict this scenario, with the massive cluster Abell 1689 being often claimed as a notable example of a highly over-concentrated halo. Shape and orientation biases in lensing studies might be on the basis of this disagreement between theory and observations. We developed a method for a full three-dimensional analysis of strong- and weak-lensing data. Surface density maps estimated from lensing are deprojected to infer the actual triaxial structure of the cluster, whose mass distribution is approximated as an ellipsoidal Navarro-Frenk-White halo with arbitrary orientation. Inversion is performed under competing a priori assumptions, integrated in the method, thanks to Bayesian statistics. We applied the method to Abell 1689. Whatever the considered priors on shape and orientation, both weak- and strong-lensing analyses found the halo to be slightly over-concentrated but still consistent with theoretical predictions. We found some evidence for a mildly-triaxial lens (minor-to-major-axis ratio � 0.5 � 0.2) with the major-axis orientated along the line of sight. Exploiting priors from N-body simulations, we found mass M200= (1.3 � 0.4) � 1015 M? and concentration c200= 10 � 3 for the weak-lensing analysis of Subaru data, M200= (1.7 � 0.3) � 1015 M? and c200= 6.1 � 0.9 for the strong-lensing analysis of multiple-image systems, and M200= (1.3 � 0.2) � 1015 M? and c200= 7.3 � 0.8 for the combined weak- plus strong-lensing analysis. Based in part on data collected at the Subaru Telescope, which is operated by the National Astronomical Society of Japan.
Sereno, Mauro; Umetsu, Keiichi
An model for dark matter: rotation curves and gravitational lensing
NASA Astrophysics Data System (ADS)
There should be two ways to describe the flat rotation curves of galaxies and cluster of galaxies. Either one can introduce a dark matter component for the matter filling the halo, or by modifying the gravity theory and give the flat rotation curve a geometrical nature. Here we adopt an model suitable for describing the effect. After matching the solution with the exterior solution, the effective density, radial and tangential pressures are obtained. Then the energy conditions and lensing effect is investigated.
Shojai, F.; Shojai, A.
CFHTLenS: mapping the large-scale structure with gravitational lensing
NASA Astrophysics Data System (ADS)
We present a quantitative analysis of the largest contiguous maps of projected mass density obtained from gravitational lensing shear. We use data from the 154 deg2 covered by the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). Our study is the first attempt to quantitatively characterize the scientific value of lensing maps, which could serve in the future as a complementary approach to the study of the dark universe with gravitational lensing. We show that mass maps contain unique cosmological information beyond that of traditional two-point statistical analysis techniques. Using a series of numerical simulations, we first show how, reproducing the CFHTLenS observing conditions, gravitational lensing inversion provides a reliable estimate of the projected matter distribution of large-scale structure. We validate our analysis by quantifying the robustness of the maps with various statistical estimators. We then apply the same process to the CFHTLenS data. We find that the two-point correlation function of the projected mass is consistent with the cosmological analysis performed on the shear correlation function discussed in the CFHTLenS companion papers. The maps also lead to a significant measurement of the third-order moment of the projected mass, which is in agreement with analytic predictions, and to a marginal detection of the fourth-order moment. Tests for residual systematics are found to be consistent with zero for the statistical estimators we used. A new approach for the comparison of the reconstructed mass map to that predicted from the galaxy distribution reveals the existence of giant voids in the dark matter maps as large as 3� on the sky. Our analysis shows that lensing mass maps are not only consistent with the results obtained by the traditional shear approach, but they also appear promising for new techniques such as peak statistics and the morphological analysis of the projected dark matter distribution.
Van Waerbeke, L.; Benjamin, J.; Erben, T.; Heymans, C.; Hildebrandt, H.; Hoekstra, H.; Kitching, T. D.; Mellier, Y.; Miller, L.; Coupon, J.; Harnois-D�raps, J.; Fu, L.; Hudson, M.; Kilbinger, M.; Kuijken, K.; Rowe, B.; Schrabback, T.; Semboloni, E.; Vafaei, S.; van Uitert, E.; Velander, M.
Constraining the minimum luminosity of high redshift galaxies through gravitational lensing
NASA Astrophysics Data System (ADS)
We simulate the effects of gravitational lensing on the source count of high redshift galaxies as projected to be observed by the Hubble Frontier Fields program and the James Webb Space Telescope (JWST) in the near future. Taking the mass density profile of the lensing object to be the singular isothermal sphere (SIS) or the Navarro-Frenk-White (NFW) profile, we model a lens residing at a redshift of zL = 0.5 and explore the radial dependence of the resulting magnification bias and its variability with the velocity dispersion of the lens, the photometric sensitivity of the instrument, the redshift of the background source population, and the intrinsic maximum absolute magnitude (Mmax) of the sources. We find that gravitational lensing enhances the number of galaxies with redshifts zgtrsim 13 detected in the angular region ?E/2 <= ? <= 2?E (where ?E is the Einstein angle) by a factor of ~ 3 and 1.5 in the HUDF (df/d?0 ~ 9 nJy) and medium-deep JWST surveys (df/d?0 ~ 6 nJy). Furthermore, we find that even in cases where a negative magnification bias reduces the observed number count of background sources, the lensing effect improves the sensitivity of the count to the intrinsic faint-magnitude cut-off of the Schechter luminosity function. In a field centered on a strong lensing cluster, observations of zgtrsim 6 and zgtrsim 13 galaxies with JWST can be used to infer this cut-off magnitude for values as faint as Mmax ~ -14.4 and -16.1 mag (Lmin ? 2.5 � 1026 and 1.2 � 1027 erg s-1 Hz-1) respectively, within the range bracketed by existing theoretical models. Gravitational lensing may therefore offer an effective way of constraining the low-luminosity cut-off of high-redshift galaxies.
Mashian, Natalie; Loeb, Abraham
The Dust-to-Gas Ratio in the Damped Ly alpha Clouds Towards the Gravitationally Lensed QSO 0957+561
NASA Technical Reports Server (NTRS)
We present HST/FOS spectra of the two bright images (A and B) of the gravitationally lensed QSO 0957+561 in the wavelength range 2200-3300 A. We find that the absorption system (Z(sub abs)) = 1.3911) near z(sub em) is a weak, damped Ly alpha system with strong Ly alpha absorption lines seen in both images. However, the H(I) column densities are different, with the line of sight to image A intersecting a larger column density. The continuum shapes of the two spectra differ in the sense that the flux level of image A increases more slowly toward shorter wavelengths than that of image B. We explain this as the result of differential reddening by dust grains in the damped Ly alpha absorber. A direct outcome of this explanation is a determination of the dust-to-gas ratio, k, in the damped Ly alpha system. We derive k = 0.55 + 0.18 for a simple 1/lambda extinction law and k = 0.31 + 0.10 for the Galactic extinction curve. For gravitationally lensed systems with damped Ly alpha absorbers, our method is a powerful tool for determining the values and dispersion of k, and the shapes of extinction curves, especially in the FUV and EUV regions. We compare our results with previous work.
Zuo, Lin; Beaver, E. A.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Lyons, R. W.
SDSS J102111.02+491330.4: A Newly discovered gravitationally lensed quasar
We report follow-up observations of two gravitational lens candidates identified in the Sloan Digital Sky Survey (SDSS) dataset. We have confirmed that SDSS J102111.02+491330.4 is a previously unknown gravitationally lensed quasar. This lens system exhibits two images of a z = 1.72 quasar, with an image separation of 1.14'' {+-} 0.04''. Optical and near-IR imaging of the system reveals the presence of the lensing galaxy between the two quasar images. Observations of SDSS J112012.12+671116.0 indicate that it is more likely a binary quasar than a gravitational lens. This system has two quasars at a redshift of z = 1.49, with an angular separation of 1.49'' {+-} 0.02''. However, the two quasars have markedly different SEDs and no lens galaxy is apparent in optical and near-IR images of this system. We also present a list of 31 SDSS lens candidates which follow-up observations have confirmed are not gravitational lenses.
Pindor, Bart; Eisenstein, Daniel J.; Gregg, Michael D.; Becker, Robert H.; Inada, Naohisa; Oguri, Masamune; Hall, Patrick B.; Johnston, David E.; Richards, Gordon T.; Schneider, Donald P.; Turner, Edwin L.; Brasi, Guido; Hinz, Philip M.; Kenworthy, Matthew A.; Miller, Doug; Barentine, J.C.; Brewington, Howard J.; Brinkmann, J.; Harvanek, Michael; Kleinman, S.J.; Krzesinski, Jurek; /Toronto U., Astron. Dept. /Arizona U., Astron. Dept. - Steward Observ. /UC, Davis /LLNL, Livermore /Tokyo U., Inst. Astron. /Tokyo U. /Princeton U. Observ. /York U., Canada /Penn State U., Astron. Astrophys. /Apache Point Observ. /Mt. Suhora Observ., Cracow /Fermilab /Chicago U., Astron. Astrophys. Ctr.
A Measurement of Gravitational Lensing of the Microwave Background Using South Pole Telescope Data
NASA Astrophysics Data System (ADS)
We use South Pole Telescope data from 2008 and 2009 to detect the non-Gaussian signature in the cosmic microwave background (CMB) produced by gravitational lensing and to measure the power spectrum of the projected gravitational potential. We constrain the ratio of the measured amplitude of the lensing signal to that expected in a fiducial ?CDM cosmological model to be 0.86 � 0.16, with no lensing disfavored at 6.3?. Marginalizing over ?CDM cosmological models allowed by the Wilkinson Microwave Anisotropy Probe (WMAP7) results in a measurement of A lens = 0.90 � 0.19, indicating that the amplitude of matter fluctuations over the redshift range 0.5 <~ z <~ 5 probed by CMB lensing is in good agreement with predictions. We present the results of several consistency checks. These include a clear detection of the lensing signature in CMB maps filtered to have no overlap in Fourier space, as well as a "curl" diagnostic that is consistent with the signal expected for ?CDM. We perform a detailed study of bias in the measurement due to noise, foregrounds, and other effects and determine that these contributions are relatively small compared to the statistical uncertainty in the measurement. We combine this lensing measurement with results from WMAP7 to improve constraints on cosmological parameters when compared to those from WMAP7 alone: we find a factor of 3.9 improvement in the measurement of the spatial curvature of the universe, ? k = -0.0014 � 0.0172; a 10% improvement in the amplitude of matter fluctuations within ?CDM, ?8 = 0.810 � 0.026; and a 5% improvement in the dark energy equation of state, w = -1.04 � 0.40. When compared with the measurement of w provided by the combination of WMAP7 and external constraints on the Hubble parameter, the addition of the lensing data improves the measurement of w by 15% to give w = -1.087 � 0.096.
van Engelen, A.; Keisler, R.; Zahn, O.; Aird, K. A.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Crawford, T. M.; Crites, A. T.; de Haan, T.; Dobbs, M. A.; Dudley, J.; George, E. M.; Halverson, N. W.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hou, Z.; Hrubes, J. D.; Joy, M.; Knox, L.; Lee, A. T.; Leitch, E. M.; Lueker, M.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Millea, M.; Mohr, J. J.; Montroy, T. E.; Natoli, T.; Padin, S.; Plagge, T.; Pryke, C.; Reichardt, C. L.; Ruhl, J. E.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Shirokoff, E.; Spieler, H. G.; Staniszewski, Z.; Stark, A. A.; Story, K.; Vanderlinde, K.; Vieira, J. D.; Williamson, R.
Weak lensing is commonly measured using shear through galaxy ellipticities or using the effect of magnification bias on galaxy number densities. Here, we report on the first detection of weak-lensing magnification with a new, independent technique using the distribution of galaxy sizes and magnitudes. These data come for free in galaxy surveys designed for measuring shear. We present the magnification estimator and apply it to an X-ray-selected sample of galaxy groups in the COSMOS Hubble Space Telescope survey. The measurement of the projected surface density {Sigma}(r) is consistent with the shear measurements within the uncertainties and has roughly 40% of the signal to noise of the latter. We discuss systematic issues and challenges to realizing the potential of this new probe of weak lensing.
Schmidt, Fabian; Rhodes, Jason [California Institute of Technology, MC 350-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Leauthaud, Alexie; Tanaka, Masayuki [Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 2778582 (Japan); Massey, Richard [Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); George, Matthew R. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Finoguenov, Alexis [Max-Planck-Institut fuer extraterrestrische Physik, Giessenbachstrasse, 85748 Garching (Germany)
A 7 deg2 survey for galaxy-scale gravitational lenses with the HST imaging archive
NASA Astrophysics Data System (ADS)
We present the results of a visual search for galaxy-scale gravitational lenses in �7 deg2 of Hubble Space Telescope (HST) images. The data set comprises the whole imaging data ever taken with the Advanced Camera for Surveys (ACS) in the filter F814W (I-band) up to 2011 August 31, i.e. 6.03 deg2 excluding the field of the Cosmic Evolution Survey which has been the subject of a separate visual search. In addition, we have searched for lenses in the whole Wide Field Camera 3 (WFC3) near-IR imaging data set in all filters (1.01 deg2) up to the same date. Our primary goal is to provide a sample of lenses with a broad range of different morphologies and lens-source brightness contrast in order to estimate a lower limit to the number of galaxy-scale strong lenses in the future Euclid survey in its VIS band. Our criteria to select lenses are purely morphological as we do not use any colour or redshift information. The final candidate selection is very conservative hence leading to a nearly pure but incomplete sample. We find 49 new lens candidates: 40 in the ACS images and 9 in the WFC3 images. Out of these, 16 candidates are secure lenses owing to their striking morphology, 21 more are very good candidates and 12 more have morphologies compatible with gravitational lensing but also compatible with other astrophysical objects such as ring and chain galaxies or mergers. Interestingly, some lens galaxies include low surface brightness galaxies, compact groups and mergers. The imaging data set is heterogeneous in depth and spans a broad range of galactic latitudes. It is therefore insensitive to cosmic variance and allows us to estimate the number of galaxy-scale strong lenses on the sky for a putative survey depth, which is the main result of this work. Because of the incompleteness of the sample, the estimated lensing rates should be taken as lower limits. Using these, we anticipate that a 15 000 deg2 space survey such as Euclid will find at least 60 000 galaxy-scale strong lenses down to a limiting AB magnitude of I = 24.5 (10?) or I = 25.8 (3?).
Pawase, R. S.; Courbin, F.; Faure, C.; Kokotanekova, R.; Meylan, G.
Fermi LAT Detection of a Hard Spectrum Gamma-ray Flare from Gravitationally Lensed Blazar S3 0218+357
NASA Astrophysics Data System (ADS)
The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope has observed a gamma-ray flare from the gravitationally lensed blazar S3 0218+357 (lens B0218+357) with an unusually hard spectrum.
Buson, S.; Cheung, C. C.
Analysis of gravitational effects on liquid lenses (ANGEL)
NASA Astrophysics Data System (ADS)
Liquid lenses have been developed as a means for fast and reliable variable-focus optics by using an adjustable curvature in a liquid-liquid interface. The use of liquid lenses also provides the benefit of reducing the number of elements in a system, and providing a degree of freedom without any moving parts. Different methods for surface curvature actuation have been developed, including aperture adjustment, mechanical actuators, stimuli-responsive hydrogels, and mechanical-wetting. Current liquid lens designs are limited to small apertures (less than 4mm) and density-matching fluids to lessen the negative effects of gravity. By creating a lens intended for use in a microgravity environment, the aperture size can be increased by orders of magnitude, and optimal fluids can be used regardless of their density. Using a large-aperture (12mm) liquid lens, image and surface metrology was conducted using a fixed-focus configuration. The Software Configurable Optical Test System (SCOTS) method was utilized to test the effect of microgravity, standard gravity, and hypergravity on the liquid lens during parabolic flights. Under standard gravity, the RMS wavefront error (WFE) was 27 wavelengths, while microgravity conditions allowed an improvement to 17 wavelengths RMS WFE. Test performance can be improved by using lower viscosity fluids or longer duration microgravity flights. The experiment also served as an engineering demonstration for the SCOTS method in an environment where other methods of optical metrology would be impossible.
Newman, Kevin; Stephens, Kyle
On the universality of microlensing in quadruple gravitational lenses
NASA Technical Reports Server (NTRS)
It is well known that multiply imaged quasars are likely to be affected by microlensing. Quadruply imaged systems are especially useful laboratories for studying microlensing because their macrolens models are relatively well constrained. We begin with analytical results for a simple family of galaxy models. These results can be used to estimate the magnifications and time delays for the quadruple systems. We compute expected brightness fluctuations due to microlensing in several such systems for a range of source sizes. Among these we treat for the first time the limiting case of a completely unresolved source. For the case of MG 0414+0534 we interpret the discrepant optical-to-radio flux ratios for the different components as the result of microlensing. On the assumption that the lensing galaxy is roughly isothermal this gives a 95% confidence upper limit on the optical source size of 10(exp 16) cm x (mean value of M)/0.1 solar mass(exp 1/2) where (M) is the average stellar mass of the lensing galaxy. For more centrally concentrated macromodels the upper limit is greater. Sufficiently long strings of photometric observations can in principle constrain the degree of concentration.
Witt, Hans J.; Mao, S.; Schechter, Paul L.
Cusp-core problem and strong gravitational lensing
NASA Astrophysics Data System (ADS)
Cosmological numerical simulations of galaxy formation have led to the cuspy density profile of a pure cold dark matter halo toward the center, which is in sharp contradiction with the observations of the rotation curves of cold dark matter-dominated dwarf and low surface brightness disk galaxies, with the latter tending to favor mass profiles with a flat central core. Many efforts have been devoted to resolving this cusp-core problem in recent years, among them, baryon-cold dark matter interactions are considered to be the main physical mechanisms erasing the cold dark matter (CDM) cusp into a flat core in the centers of all CDM halos. Clearly, baryon-cold dark matter interactions are not customized only for CDM-dominated disk galaxies, but for all types, including giant ellipticals. We first fit the most recent high resolution observations of rotation curves with the Burkert profile, then use the constrained core size-halo mass relation to calculate the lensing frequency, and compare the predicted results with strong lensing observations. Unfortunately, it turns out that the core size constrained from rotation curves of disk galaxies cannot be extrapolated to giant ellipticals. We conclude that, in the standard cosmological paradigm, baryon-cold dark matter interactions are not universal mechanisms for galaxy formation, and therefore, they cannot be true solutions to the cusp-core problem.
Li, Nan; Chen, Da-Ming
Weak Lensing Calibration of the Galaxy Cluster Mass Scale in the South Pole Telescope Sunyaev-Zel'dovich Survey
NASA Astrophysics Data System (ADS)
The South Pole Telescope (SPT) has detected clusters above a nearly uniform mass threshold over an extremely broad range in redshift by searching for the Sunyaev-Zel'dovich effect. The observed abundance of clusters from such a well selected sample is directly sensitive to the growth function of matter perturbations over the majority of the history of the universe, and provides powerful constraints on dark energy with systematics that are complementary to traditional distance-based measures. The dominant source of uncertainty on dark energy constraints from this technique is our estimate of total cluster mass. We have observed 19 SPT clusters at 0.3 < z < 0.6 with Megacam on the Magellan-Clay 6.5 m telescope, and 14 SPT clusters at 0.6 < z < 1.3 with HST-ACS, to estimate total mass for these ~ (3-10)x10^14 Msun systems with weak gravitational lensing. We present results on the scaling of Y_SZ and Y_X with total mass, as well as the improvement in cosmological constraints afforded by the weak lensing data.
High, F. W.; South Pole Telescope Team
Strong and Weak Lensing United III: Measuring the Mass Distribution of the Merging Galaxy Cluster 1E0657-56
The galaxy cluster 1E0657-56 (z = 0.296) is remarkably well-suited for addressing outstanding issues in both galaxy evolution and fundamental physics. We present a reconstruction of the mass distribution from both strong and weak gravitational lensing data. Multi-color, high-resolution HST ACS images allow detection of many more arc candidates than were previously known, especially around the subcluster. Using the known redshift of one of the multiply imaged systems, we determine the remaining source redshifts using the predictive power of the strong lens model. Combining this information with shape measurements of ''weakly'' lensed sources, we derive a high-resolution, absolutely-calibrated mass map, using no assumptions regarding the physical properties of the underlying cluster potential. This map provides the best available quantification of the total mass of the central part of the cluster. We also confirm the result from Clowe et al. (2004, 2006a) that the total mass does not trace the baryonic mass.
Bradac, Marusa; Clowe, Douglas; Gonzalez, Anthony H.; Marshall, Phil; Forman, William; Jones, Christine; Markevitch, Maxim; Randall, Scott; Schrabback, Tim; Zaritsky, Dennis; /KIPAC, Menlo Park /Bonn, Inst. Astrophys. /Arizona U., Astron. Dept. - Steward Observ. /Florida U. /Harvard-Smithsonian Ctr. Astrophys.
X-ray and Weak Lensing Masses for a Sample of 50 Relaxed and Non-Relaxed Clusters of Galaxies
NASA Astrophysics Data System (ADS)
We present an updated, recalibrated, multiwavelength, X-ray + weak lensing measurement of the mass profiles for 50 rich systems of galaxies. We find that our weak gravitational lensing masses, calibrated with state-of-the-art shear testing simulations, are 18% +/- 4% higher than those found for the clusters in the Planck satellite sample. Using the Joint Analysis of Cluster Observations codebase, we simultaneously model the baryonic and nonbaryonic matter profiles in these systems, deriving joint constraints on the gas entropy, pressure, metallicity, and dark matter distributions. Simultaneous analysis of Chandra and XMM-Newton data where both are available allows us to constrain these profiles over nearly two decades in radius. We find clusters with low BCG-to-X-ray center offsets form a remarkably regular sample, with NFW dark matter profiles and gas fraction values that are consistent with the cosmological value. Clusters with low central gas entropy exhibit a similar trend, and do so with an intrinsic scatter that is consistent with zero. Non-relaxed clusters, on the other hand---those with offset BCGs and high central entropies---exhibit significant scatter and have mass profiles inconsistent with the NFW value (most likely due to strong violations of spherical symmetry).
Mahdavi, Andisheh; Hoekstra, Henk; Babul, Arif
Towards an understanding of dark matter: Precise gravitational lensing analysis complemented by robust photometric redshifts
NASA Astrophysics Data System (ADS)
The goal of thesis is to help scientists resolve one of the great mysteries of our time: the nature of Dark Matter. Dark Matter is currently believed to make up over 80% of the material in our universe, yet we have so far inferred but a few of its basic properties. Here we study the Dark Matter surrounding a galaxy cluster, Abell 1689, via the most direct method currently available--gravitational lensing. Abell 1689 is a "strong" gravitational lens, meaning it produces multiple images of more distant galaxies. The observed positions of these images can be measured very precisely and act as a blueprint allowing us to reconstruct the Dark Matter distribution of the lens. Until now, such mass models of Abell 1689 have reproduced the observed multiple images well but with significant positional offsets. Using a new method we develop here, we obtain a new mass model which perfectly reproduces the observed positions of 168 knots identified within 135 multiple images of 42 galaxies. An important ingredient to our mass model is the accurate measurement of distances to the lensed galaxies via their photometric redshifts. Here we develop tools which improve the accuracy of these measurements based on our study of the Hubble Ultra Deep Field, the only image yet taken to comparable depth as the magnified regions of Abell 1689. We present results both for objects in the Hubble Ultra Deep Field and for galaxies gravitationally lensed by Abell 1689. As part of this thesis, we also provide reviews of Dark Matter and Gravitational Lensing, including a chapter devoted to the mass profiles of Dark Matter halos realized in simulations. The original work presented here was performed primarily by myself under the guidance of Narciso Ben�tez and Holland Ford as a member of the Advanced Camera for Surveys GTO Science Team at Johns Hopkins University and the Instituto de Astrofisica de Andalucfa. My advisors served on my thesis committee along with Rick White, Gabor Domokos, and Steve Zelditch.
Coe, Daniel Aaron
Cosmological constraints from strong gravitational lensing in clusters of galaxies.
Current efforts in observational cosmology are focused on characterizing the mass-energy content of the universe. We present results from a geometric test based on strong lensing in galaxy clusters. Based on Hubble Space Telescope images and extensive ground-based spectroscopic follow-up of the massive galaxy cluster Abell 1689, we used a parametric model to simultaneously constrain the cluster mass distribution and dark energy equation of state. Combining our cosmological constraints with those from x-ray clusters and the Wilkinson Microwave Anisotropy Probe 5-year data gives Omega(m) = 0.25 +/- 0.05 and w(x) = -0.97 +/- 0.07, which are consistent with results from other methods. Inclusion of our method with all other available techniques brings down the current 2sigma contours on the dark energy equation-of-state parameter w(x) by approximately 30%. PMID:20724628
Jullo, Eric; Natarajan, Priyamvada; Kneib, Jean-Paul; D'Aloisio, Anson; Limousin, Marceau; Richard, Johan; Schimd, Carlo
Nova Geminorum 1912 and the origin of the idea of gravitational lensing
NASA Astrophysics Data System (ADS)
Einstein's early calculations of gravitational lensing, contained in a scratch notebook and dated to the spring of 1912, are reexamind. A hitherto unknown letter by Einstein suggests that he entertained the idea of explaining the phenomenon of new stars by gravitational lensing in the fall of 1915 much more seriously than was previously assumed. A reexamination of the relevant calculations by Einstein shows that, indeed, at least some of them most likely date from early October 1915. But in support of earlier historical interpretation of Einstein's notes, it is argued that the appearance of Nova Geminorum 1912 (DN Gem) in March 1912 may, in fact, provide a relevant context and motivation for Einstein's lensing calculations on the occasion of his first meeting with Erwin Freundlich during a visit in Berlin in April 1912. The author also comments on the significance of Einstein's consideration of graviatational lensing in the fall of 1915 for the reconstruction of Einstein's final steps in his path towards general relativity.
Sauer, T.
The best gravitational lenses for detecting distant galaxies are those with the largest mass concentrations and the most advantageous configurations of that mass along the line of sight. Our new method for finding such gravitational telescopes uses optical data to identify projected concentrations of luminous red galaxies (LRGs). LRGs are biased tracers of the underlying mass distribution, so lines of sight with the highest total luminosity in LRGs are likely to contain the largest total mass. We apply this selection technique to the Sloan Digital Sky Survey and identify the 200 fields with the highest total LRG luminosities projected within a 3.'5 radius over the redshift range 0.1 {<=} z {<=} 0.7. The redshift and angular distributions of LRGs in these fields trace the concentrations of non-LRG galaxies. These fields are diverse; 22.5% contain one known galaxy cluster and 56.0% contain multiple known clusters previously identified in the literature. Thus, our results confirm that these LRGs trace massive structures and that our selection technique identifies fields with large total masses. These fields contain two to three times higher total LRG luminosities than most known strong-lensing clusters and will be among the best gravitational lensing fields for the purpose of detecting the highest redshift galaxies.
Wong, Kenneth C.; Zabludoff, Ann I. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Ammons, S. Mark [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); Keeton, Charles R. [Department of Physics and Astronomy, Rutgers University, 136 Frelinghuysen Road, Piscataway, NJ 08854 (United States); Hogg, David W. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States)
Weak cosmic censorship in gravitational collapse with astrophysical parameter values
NASA Astrophysics Data System (ADS)
The possible violation of the weak cosmic censorship hypothesis in astrophysical phenomena can provide us with information about trans-Planckian physics through observations. We present negative evidence, however, that one should not expect such a possibility at least when the deviation from spherical symmetry is negligible and the parameter values of collapse are astrophysically reasonable. Taking the Lema�tre-Tolman-Bondi solution as the model most likely to counter the weak hypothesis, we show that the mass ({? } 1.5 M_? ) and density ({? } 1.5� 10^{15} {g/cm}^3) of the collapsing object produce a gravitational field strong enough to capture any null rays soon after emanating from the singularity.
Miyamoto, Umpei; Jhingan, Sanjay; Harada, Tomohiro
Dynamical Confirmation of Sloan Digital Sky Survey Weak-lensing Scaling Laws
Galaxy masses can be estimated by a variety of methods, each applicable in different circumstances and each suffering from different systematic uncertainties. Confirmation of results obtained by one technique with analysis by another is particularly important. Recent Sloan Digital Sky Survey weak-lensing measurements of the projected mass correlation function reveal a linear relation between galaxy luminosities and the depth of
Erin Scott Sheldon; David Johnston; Eva K. Grebel; Francisco Prada; Hans-Walter Rix; Neta A. Bahcall; J. Brinkmann; Istv�n Csabai; Masataka Fukugita; D. Q. Lamb; Donald G. York
Weak lensing and dark energy: The impact of dark energy on nonlinear dark matter clustering
We examine the influence of percent-level dark energy corrections to the nonlinear matter power spectrum on constraints of the dark energy equation of state from future weak lensing probes. We explicitly show that a poor approximation (off by > or approx.10%) to the nonlinear corrections causes a > or approx. 1{sigma} bias on the determination of the dark energy equation of state. Future weak lensing surveys must therefore incorporate dark energy modifications to the nonlinear matter power spectrum accurate to the percent-level, to avoid introducing significant bias in their measurements. For the WMAP5 cosmology, the more accurate power spectrum is more sensitive to dark energy properties, resulting in a factor of 2 improvement in dark energy equation of state constraints. We explore the complementary constraints on dark energy from future weak lensing and supernova surveys. A space-based, Joint Dark Energy Mission-like survey measures the equation of state in five independent redshift bins to {approx}10%, while this improves to {approx}5% for a wide-field ground-based survey like the Large Synoptic Survey Telescope. These constraints are contingent upon our ability to control weak lensing systematic uncertainties to the sub-percent level.
Joudaki, Shahab; Cooray, Asantha; Holz, Daniel E. [Center for Cosmology, Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
Construction of the one-point PDF of the local aperture mass in weak lensing maps
We present a general method for the reconstruction of the one-point Probability Distribution Function of the local aperture mass in weak lensing maps. Exact results, that neglect the lens-lens coupling and departure from the Born approximation, are derived for both the quasilinear regime at leading order and the strongly nonlinear regime assuming the tree hierarchical model is valid. We describe
Francis Bernardeau; Patrick Valageas
Gravitational Lensing of the Microwave Background in the 2500 Square Degree SPT Survey
NASA Astrophysics Data System (ADS)
The South Pole Telescope (SPT) is a 10-meter microwave background telescope located at the geographic South Pole that completed a deep multi-band survey of �2,500 square degrees of the southern sky in Fall 2011. The high angular resolution and sensitivity enable a reconstruction of the matter potential integrated toward the last scattering surface, effectively weighing the Hubble volume. The inferred lensing potential power spectrum is a sensitive probe of cosmological structure growth and geometry beyond the temperature and polarization power spectra. I will present the results of our analysis using an optimal trispectrum estimator to achieve the highest signal-to-noise measurement of gravitational lensing of the CMB to date. Careful control of astrophysical and instrumental contaminants of the non-Gaussian signature of lensing allow us to place robust constraints on dark energy and the sum of the masses of neutrinos. I will also discuss how the correlation of our lensing maps with galaxy clustering surveys can yield novel astrophysical and cosmological information. The talk will conclude by previewing the potential of joint analyses of our lensing measurements with Planck satellite data, as well as of new data currently being collected by SPTpol.
Zahn, Oliver
Mock weak lensing analysis of simulated galaxy clusters: bias and scatter in mass and concentration
NASA Astrophysics Data System (ADS)
We quantify the bias and scatter in galaxy cluster masses M200 and concentrations c derived from an idealized mock weak gravitational lensing (WL) survey, and their effect on the cluster mass-concentration relation. For this, we simulate WL distortions on a population of background galaxies due to a large (?3000) sample of galaxy cluster haloes extracted from the Millennium Simulation at z? 0.2. This study takes into account the influence of shape noise, cluster substructure and asphericity as well as correlated large-scale structure, but not uncorrelated large-scale structure along the line of sight and observational effects (e.g. the source redshift distribution and measurement, and measurement of galaxy ellipticities). We find a small, but non-negligible, negative median bias in both mass and concentration at a level of �5 per cent, the exact value depending both on cluster mass and on radial survey range. Both the mass and concentration derived from WL show considerable scatter about their true values. This scatter has, even for the highest mass clusters of M200 > 1014.8 M?, a level of �30 per cent and �20 per cent for concentration and mass, respectively, and increases strongly with decreasing cluster mass. For a typical survey analysing 30 galaxies per arcmin2 over a radial range from 30 arcsec to 15 arcmin from the cluster centre, the derived M200-c relation has a slope and normalization too low compared to the underlying true (3D) relation by �40 per cent and �15 per cent, respectively. The scatter and bias in mass are shown to reflect a departure at large radii of the true WL shear/matter distribution of the simulated clusters from the NFW profile adopted in modelling the mock observations. Orientation of the triaxial cluster haloes dominates the concentration scatter (except at low masses, where galaxy shape noise becomes dominant), while the bias in c is mostly due to substructure within the virial radius.
Bah�, Yannick M.; McCarthy, Ian G.; King, Lindsay J.
CALCLENS: Weak lensing simulations for large-area sky surveys and second-order effects in cosmic shear power spectra
NASA Astrophysics Data System (ADS)
I present a new algorithm, CALCLENS, for efficiently computing weak gravitational lensing shear signals from large N-body light cone simulations over a curved sky. This new algorithm properly accounts for the sky curvature and boundary conditions, is able to produce redshift- dependent shear signals including corrections to the Born approximation by using multiple- plane ray tracing, and properly computes the lensed images of source galaxies in the light cone. The key feature of this algorithm is a new, computationally efficient Poisson solver for the sphere that combines spherical harmonic transform and multigrid methods. As a result, large areas of sky (~10,000 square degrees) can be ray traced efficiently at high-resolution using only a few hundred cores. Using this new algorithm and curved-sky calculations that only use a slower but more accurate spherical harmonic transform Poisson solver, I study the convergence, shear E-mode, shear B-mode and rotation mode power spectra. Employing full-sky E/B-mode decompositions, I confirm that the numerically computed shear B-mode and rotation mode power spectra are equal at high accuracy ( ? 1%) as expected from perturbation theory up to second order. Coupled with realistic galaxy populations placed in large N-body light cone simulations, this new algorithm is ideally suited for the construction of synthetic weak lensing shear catalogs to be used to test for systematic effects in data analysis procedures for upcoming large-area sky surveys. The implementation presented in this work, written in C and employing widely available software libraries to maintain portability, is publicly available at http://code.google.com/p/calclens.
Becker, Matthew Rand
Gravitational lensing effects of vacuum strings - Exact solutions
NASA Technical Reports Server (NTRS)
Exact interior and exterior solutions to Einstein's field equations are derived for vacuum strings. The exterior solution for a uniform density vacuum string corresponds to a conical space while the interior solution is that of a spherical cap. For Mu equals 0-1/4 the external metric is ds-squared = -dt-squared + dr-squared + (1-4 Mu)-squared r-squared dphi-squared + dz-squared, where Mu is the mass per unit length in the string in Planck masses per Planck length. A maximum mass per unit length for a string is 6.73 x 10 to the 27th g/cm. It is shown that strings cause temperature fluctuations in the cosmic microwave background and produce equal brightness double QSO images separated by up to several minutes of arc. Formulae for lensing probabilities, image splittings, and time delays are derived for strings in a realistic cosmological setting. String searches using ST, the VLA, and the COBE satellite are discussed.
Gott, J. R., III
Measurement of Gravitational Lens Time Delays with LSST.
National Technical Information Service (NTIS)
The proposed Large Synoptic Survey Telescope will be the first to explore multiple dark energy probes simultaneously, including baryon acoustic oscillations, weak lensing, and strong gravitational lensing. The large data sample, covering the entire visibl...
L. A. Kirkby
Weak lensing by intergalactic ministructures in quadruple lens systems: simulation and detection
NASA Astrophysics Data System (ADS)
We investigate the weak lensing effects of line-of-sight structures on quadruple images in quasar-galaxy strong lens systems based on N-body and ray-tracing simulations that can resolve haloes with a mass of �105 M?. The intervening haloes and voids disturb the magnification ratios of lensed images as well as their relative positions due to lensing. The magnification ratios typically change by O(10 per cent) when the shifts of relative angular positions of lensed images are constrained to <0.004 arcsec. The constrained amplitudes of projected density perturbations due to line-of-sight structures are O(108) M? arcsec- 2. These results are consistent with our new analytical estimate based on the two-point correlation of density fluctuations. The observed mid-infrared flux ratios for six quasar-galaxy lens systems with quadruple images agree well with the numerically estimated values without taking into account subhalos residing in the lensing galaxies. We find that the constrained mean amplitudes of projected density perturbations in the line of sight are negative, which suggests that the fluxes of lensed images are perturbed mainly by minivoids and minihaloes in underdense regions. We derive a new fitting formula for estimating the probability distribution function of magnification perturbation. We also find that the mean amplitude of magnification perturbation roughly equals the standard deviation regardless of the model parameters.
Takahashi, Ryuichi; Inoue, Kaiki Taro
Subaru Weak-lensing Survey of Dark Matter Subhalos in the Coma Cluster: Subhalo Mass Function and Statistical Properties
NASA Astrophysics Data System (ADS)
We present a 4 deg2 weak gravitational lensing survey of subhalos in the very nearby Coma cluster using the Subaru/Suprime-Cam. The large apparent size of cluster subhalos allows us to measure the mass of 32 subhalos detected in a model-independent manner, down to the order of 10-3 of the virial mass of the cluster. Weak-lensing mass measurements of these shear-selected subhalos enable us to investigate subhalo properties and the correlation between subhalo masses and galaxy luminosities for the first time. The mean distortion profiles stacked over subhalos show a sharply truncated feature which is well-fitted by a Navarro-Frenk-White (NFW) mass model with the truncation radius, as expected due to tidal destruction by the main cluster. We also found that subhalo masses, truncation radii, and mass-to-light ratios decrease toward the cluster center. The subhalo mass function, dn/dln M sub, in the range of 2 orders of magnitude in mass, is well described by a single power law or a Schechter function. Best-fit power indices of 1.09^{+0.42}_{-0.32} for the former model and 0.99_{-0.23}^{+0.34} for the latter, are in remarkable agreement with slopes of ~0.9-1.0 predicted by the cold dark matter paradigm. The tangential distortion signals in the radial range of 0.02-2 h -1 Mpc from the cluster center show a complex structure which is well described by a composition of three mass components of subhalos, the NFW mass distribution as a smooth component of the main cluster, and a lensing model from a large scale structure behind the cluster. Although the lensing signals are 1 order of magnitude lower than those for clusters at z ~ 0.2, the total signal-to-noise ratio, S/N = 13.3, is comparable, or higher, because the enormous number of background source galaxies compensates for the low lensing efficiency of the nearby cluster. Based on data collected from the Subaru Telescope and obtained from SMOKA, operated by the Astronomy Data Center, National Astronomical Observatory of Japan.
Okabe, Nobuhiro; Futamase, Toshifumi; Kajisawa, Masaru; Kuroshima, Risa
Evidence for gravitational lensing of the cosmic microwave background polarization from cross-correlation with the cosmic infrared background.
We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0? and indication of the presence of a lensing B-mode signal at a significance of 2.3?. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics. PMID:24745402
Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Borys, C; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Leitch, E M; Linder, E; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Poletti, D; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Rotermund, K; Schanning, I; Schenck, D E; Sherwin, B D; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tikhomirov, A; Tomaru, T; Wilson, B; Yadav, A; Zahn, O
Automated Detection of Galaxy-Scale Gravitational Lenses in High-Resolution Imaging Data
NASA Astrophysics Data System (ADS)
We expect direct lens modeling to be the key to successful and meaningful automated strong galaxy-scale gravitational lens detection. We have implemented a lens-modeling "robot" that treats every bright red galaxy (BRG) in a large imaging survey as a potential gravitational lens system. Having optimized a simple model for "typical" galaxy-scale gravitational lenses, we generate four assessments of model quality that are then used in an automated classification. The robot infers from these four data the lens classification parameter H that a human would have assigned; the inference is performed using a probability distribution generated from a human-classified training set of candidates, including realistic simulated lenses and known false positives drawn from the Hubble Space Telescope (HST) Extended Groth Strip (EGS) survey. We compute the expected purity, completeness, and rejection rate, and find that these statistics can be optimized for a particular application by changing the prior probability distribution for H; this is equivalent to defining the robot's "character." Adopting a realistic prior based on expectations for the abundance of lenses, we find that a lens sample may be generated that is ~100% pure, but only ~20% complete. This shortfall is due primarily to the oversimplicity of the model of both the lens light and mass. With a more optimistic robot, ~90% completeness can be achieved while rejecting ~90% of the candidate objects. The remaining candidates must be classified by human inspectors. Displaying the images used and produced by the robot on a custom "one-click" web interface, we are able to inspect and classify lens candidates at a rate of a few seconds per system, suggesting that a future 1000 deg2 imaging survey containing 107 BRGs, and some 104 lenses, could be successfully, and reproducibly, searched in a modest amount of time. We have verified our projected survey statistics, albeit at low significance, using the HST EGS data, discovering four new lens candidates in the process.
Marshall, Philip J.; Hogg, David W.; Moustakas, Leonidas A.; Fassnacht, Christopher D.; Brada?, Maru�a; Schrabback, Tim; Blandford, Roger D.
CFHTLS weak-lensing constraints on the neutrino masses
NASA Astrophysics Data System (ADS)
Context: Oscillation experiments yield strong evidence that at least some neutrinos are massive. As a hot dark-matter component, massive neutrinos should modify the expansion history of the Universe as well as the evolution of cosmological perturbations, in a different way from cold dark matter or dark energy. Aims: We use the latest release of CFHTLS cosmic-shear data to constrain the sum of the masses sum m_? of neutrinos, assuming three degenerate mass states. We also consider a joint analysis including other cosmological observables, notably CMB anisotropies, baryonic acoustic oscillations, and distance modulus from type Ia supernovae. Methods: Combining CAMB with a lensing code, we compute the aperture mass variance using a suitable recipe to deal with matter perturbations in the non-linear regime. The statistical analysis is performed by sampling an 8-dimensional likelihood on a regular grid as well as using the importance sampling technique. Results: We obtain the first constraint on neutrino masses based on cosmic-shear data, and combine CFHTLS with WMAP, SDSS, 2dFGRS, Gold-set, and SNLS data. The joint analysis yields 0.03 eV < sum m_? < 0.54 eV at the 95% confidence level. The preference for massive neutrinos vanishes when systematics are included. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at TERAPIX and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS.
Tereno, I.; Schimd, C.; Uzan, J.-P.; Kilbinger, M.; Vincent, F. H.; Fu, L.
Weak lensing analysis of SZ-selected clusters of galaxies from the SPT and Planck surveys
NASA Astrophysics Data System (ADS)
We present the weak lensing analysis of the Wide-Field Imager Sunyaev-Zel'dovich Cluster of Galaxy (WISCy) sample, a set of 12 clusters of galaxies selected for their Sunyaev-Zel'dovich (SZ) effect. After developing new and improved methods for background selection and determination of geometric lensing scaling factors from absolute multiband photometry in cluster fields, we compare the weak lensing mass estimate with public X-ray and SZ data. We find consistency with hydrostatic X-ray masses with no significant bias, no mass dependent bias and less than 20 per cent intrinsic scatter and constrain f_{{gas},500c}=0.128^{+0.029}_{-0.023}. We independently calibrate the South Pole Telescope significance-mass relation and find consistency with previous results. The comparison of weak lensing mass and Planck Compton parameters, whether extracted self-consistently with a mass-observable relation (MOR) or using X-ray prior information on cluster size, shows significant discrepancies. The deviations from the MOR strongly correlate with cluster mass and redshift. This could be explained either by a significantly shallower than expected slope of Compton decrement versus mass and a corresponding problem in the previous X-ray based mass calibration, or a size or redshift dependent bias in SZ signal extraction.
Gruen, D.; Seitz, S.; Brimioulle, F.; Kosyra, R.; Koppenhoefer, J.; Lee, C.-H.; Bender, R.; Riffeser, A.; Eichner, T.; Weidinger, T.; Bierschenk, M.
Wavelet Helmholtz decomposition for weak lensing mass map reconstruction
NASA Astrophysics Data System (ADS)
To derive the convergence field from the gravitational shear ? of the background galaxy images, the classical methods require a convolution of the shear to be performed over the entire sky, usually expressed by the fast Fourier transform (FFT). However, it is not optimal for an imperfect geometry survey. Furthermore, FFT implicitly uses periodic conditions that introduce errors into the reconstruction. A method has been proposed that relies on computation of an intermediate field u that combines the derivatives of ? and on convolution with a Green kernel. In this paper, we study the wavelet Helmholtz decomposition as a new approach to reconstructing the dark matter mass map. We show that a link exists between the Helmholtz decomposition and the electric and magnetic component separation. We introduce a new wavelet construction that has a property that gives us more flexibility in handling the border problem, and we propose a new method of reconstructing the dark matter mass map in the wavelet space. A set of experiments based on noise-free images illustrates that this Wavelet Helmholtz decomposition reconstructs the borders better than all other existing methods.
Deriaz, E.; Starck, J.-L.; Pires, S.
Effects of gravitational lensing and companion motion on the binary pulsar timing
The measurement of the Shapiro time delay in binary pulsar systems with highly-inclined orbit can be affected both by the motion of the pulsar's companion because of the finite time it takes a photon to cross the binary, and by the gravitational light bending if the orbit is sufficiently edge-on relative to the line of sight. Here we calculate the effect of retardation due to the companion's motion on various time delays in pulsar binaries, including the Shaipro delay, the geometric lensing delay, and the lens-induced delays associated with the pulsar rotation. Our results can be applied to systems so highly inclined that near conjunction gravitational lensing of the pulsar radiation by the companion becomes important (the recently discovered double pulsar system J0737-3039 may exemplify such a system). To the leading order, the effect of retardation is to shift all the delay curves backward in time around the orbit conjunction, without affecting the shape and amplitude of the curves. The time shift is of order the photon orbit crossing time, and ranges from a second to a few minutes for the observed binary pulsar systems. In the double pulsar system J0737-3039, the motion of the companion may also affect the interpretation of the recent correlated interstellar scintillation measurements. Finally, we show that lensing sets an upper limit on the magnitude of the frame-dragging time delay caused by the companion's spin, and makes this delay unobservable in stellar-mass binary pulsar systems.
Rafikov, Roman R.; Lai Dong [CITA, McLennan Physics Labs, 60 St. George St., University of Toronto, Toronto, ON M5S 3H8 (Canada); Department of Astronomy, Cornell University, Ithaca, New York 14853 (United States)
We use South Pole Telescope data from 2008 and 2009 to detect the non-Gaussian signature in the cosmic microwave background (CMB) produced by gravitational lensing and to measure the power spectrum of the projected gravitational potential. We constrain the ratio of the measured amplitude of the lensing signal to that expected in a fiducial {Lambda}CDM cosmological model to be 0.86 {+-} 0.16, with no lensing disfavored at 6.3{sigma}. Marginalizing over {Lambda}CDM cosmological models allowed by the Wilkinson Microwave Anisotropy Probe (WMAP7) results in a measurement of A{sub lens} 0.90 {+-} 0.19, indicating that the amplitude of matter fluctuations over the redshift range 0.5 {approx}< z {approx}< 5 probed by CMB lensing is in good agreement with predictions. We present the results of several consistency checks. These include a clear detection of the lensing signature in CMB maps filtered to have no overlap in Fourier space, as well as a 'curl' diagnostic that is consistent with the signal expected for {Lambda}CDM. We perform a detailed study of bias in the measurement due to noise, foregrounds, and other effects and determine that these contributions are relatively small compared to the statistical uncertainty in the measurement. We combine this lensing measurement with results from WMAP7 to improve constraints on cosmological parameters when compared to those from WMAP7 alone: we find a factor of 3.9 improvement in the measurement of the spatial curvature of the universe, {Omega}{sub k} = -0.0014 {+-} 0.0172; a 10% improvement in the amplitude of matter fluctuations within {Lambda}CDM, {sigma}{sub 8} = 0.810 {+-} 0.026; and a 5% improvement in the dark energy equation of state, w = -1.04 {+-} 0.40. When compared with the measurement of w provided by the combination of WMAP7 and external constraints on the Hubble parameter, the addition of the lensing data improves the measurement of w by 15% to give w -1.087 {+-} 0.096.
Van Engelen, A.; De Haan, T.; Dobbs, M. A.; Dudley, J.; Holder, G. P. [Department of Physics, McGill University, 3600 Rue University, Montreal, Quebec H3A 2T8 (Canada); Keisler, R.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Crawford, T. M.; Crites, A. T.; Hoover, S. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Zahn, O. [Berkeley Center for Cosmological Physics, Department of Physics, University of California, and Lawrence Berkeley National Labs, Berkeley, CA 94720 (United States); Aird, K. A. [University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Cho, H. M. [NIST Quantum Devices Group, 325 Broadway Mailcode 817.03, Boulder, CO 80305 (United States); George, E. M.; Holzapfel, W. L. [Department of Physics, University of California, Berkeley, CA 94720 (United States); Halverson, N. W. [Department of Astrophysical and Planetary Sciences and Department of Physics, University of Colorado, Boulder, CO 80309 (United States); Hou, Z. [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); and others
Gravitational lensing as signal and noise in Lyman-{alpha} forest measurements
In Lyman-{alpha} forest measurements it is generally assumed that quasars are mere background light sources which are uncorrelated with the forest. Gravitational lensing of the quasars violates this assumption. This effect leads to a measurement bias, but more interestingly it provides a valuable signal. The lensing signal can be extracted by correlating quasar magnitudes with the flux-power spectrum and with the flux decrement. These correlations will be challenging to measure but their detection provides a direct measure of how features in the Lyman-{alpha} forest trace the underlying mass density field. Observing them will test the fundamental hypothesis that fluctuations in the forest are predominantly driven by fluctuations in mass, rather than in the ionizing background, helium reionization, or winds. We discuss ways to disentangle the lensing signal from other sources of such correlations, including dust, continuum, and background residuals. The lensing-induced measurement bias arises from sample selection: one preferentially collects spectra of magnified quasars which are behind overdense regions. This measurement bias is {approx}0.1-1% for the flux-power spectrum, optical depth, and the flux probability distribution. Since the effect is systematic, quantities such as the amplitude of the flux-power spectrum averaged across scales should be interpreted with care.
LoVerde, Marilena [Institute for Advanced Study, Princeton, New Jersey 08540 (United States); ISCAP and Department of Physics, Columbia University, New York, New York 10027 (United States); Marnerides, Stefanos [ISCAP and Department of Physics, Columbia University, New York, New York 10027 (United States); Hui, Lam [Institute for Advanced Study, Princeton, New Jersey 08540 (United States); ISCAP and Department of Physics, Columbia University, New York, New York 10027 (United States); CCPP and Department of Physics, New York University, New York 10003 (United States); Menard, Brice [Canadian Institute for Theoretical Astrophysics, Toronto, Ontario M5S 3H8 (Canada); Lidz, Adam [Center for Astrophysics, Harvard University, Cambridge, Massachusetts 02138 (United States); Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (United States)
Spin effects in gravitational radiation back reaction. I. The Lense-Thirring approximation
NASA Astrophysics Data System (ADS)
The gravitational radiation back reaction effects are considered in the Lense-Thirring approximation. New methods for parametrizing the orbit and for averaging the instantaneous radiative losses are developed. To first order in the spin S of the black hole, both in the absence and in the presence of gravitational radiation, a complete description of the test-particle orbit is given. This is achieved by two improvements over the existing descriptions: first, by introducing new angle variables with a straightforward geometrical meaning; second, by finding a new parametrization of a generic orbit, which assures that the integration over a radial period can be done in an especially simple way, by applying the residue theorem. The instantaneous gravitational radiation losses of the system are computed using the formulation of Blanchet, Damour and Iyer. All losses are given both in terms of the dynamical constants of motion and the properly defined orbital elements a, e, ? and ?0. The radiative losses of the constants characterizing the Lense-Thirring motion, when suitably converted, are in agreement with earlier results of Kidder, Will and Wiseman, Ryan and Shibata. In addition, the radiative losses of two slowly changing orbital elements ?0,?0 are given in order to complete the characterization of the orbit.
Gergely, L�szl� �.; Perj�s, Zolt�n I.; Vas�th, M�ty�s
A test of the Suyama-Yamaguchi inequality from weak lensing
NASA Astrophysics Data System (ADS)
We investigate the weak lensing signature of primordial non-Gaussianities of the local type by constraining the magnitude of the weak convergence bi- and trispectra expected for the Euclid weak lensing survey. Starting from expressions for the weak convergence spectra, bispectra and trispectra, whose relative magnitudes we investigate as a function of scale, we compute their respective signal-to-noise ratios by relating the polyspectra's amplitude to their Gaussian covariance using a Monte Carlo technique for carrying out the configuration space integrations. In computing the Fisher matrix on the non-Gaussianity parameters fNL, gNL and ?NL with a very similar technique, we can derive pieces of Bayesian evidence for a violation of the Suyama-Yamaguchi (SY) relation ?NL ? (6fNL/5)2 as a function of the true fNL- and ?NL-values and show that the relation can be probed down to levels of fNL ? 102 and ?NL ? 105. In a related study, we derive analytical expressions for the probability density that the SY relation is exactly fulfilled, as required by models in which any one field generates the perturbations. We conclude with an outlook on the levels of non-Gaussianity that can be probed with tomographic lensing surveys.
Grassi, Alessandra; Heisenberg, Lavinia; Byrnes, Christian T.; Sch�fer, Bj�rn Malte
Constraint on the Cosmological Constant from Gravitational Lensing in AN Evolutionary Model of Galaxies
NASA Astrophysics Data System (ADS)
We study the effect of the cosmological constant on the statistical properties of gravitational lenses in flat cosmologies (?0+?0=1). It is shown that some of the lens observables are strongly affected by the cosmological constant, especially in a low-density universe, and its existence might be inferred by a statistical study of the lenses. In particular, the optical depth of the lens distribution may be used best for this purpose without depending much on the lens model. We calculate the optical depth (probability of a beam encountering a lens event) for a source in a new picture of galaxy evolution based on number evolution in addition to pure luminosity evolution. It seem that present-day galaxies result from the merging of a large number of building blocks. We have tried to put a limit on the cosmological constant in this new picture of galaxy evolution. This evolutionary model of galaxies permits a larger value of the cosmological constant.
Jain, Deepak; Panchapakesan, N.; Mahajan, S.; Bhatia, V. B.
Strong gravitational lensing in a rotating Kaluza-Klein black hole with squashed horizons
NASA Astrophysics Data System (ADS)
We have investigated the strong gravitational lensing in a rotating squashed Kaluza-Klein (KK) black hole spacetime. Our result show that the strong gravitational lensings in the rotating squashed KK black hole spacetime have some distinct behaviors from those in the backgrounds of the four-dimensional Kerr black hole and of the squashed KK G�del black hole. In the rotating squashed KK black hole spacetime, the marginally circular photon radius ? ps , the coefficient , , the deflection angle ?( ?) in the ? direction and the corresponding observational variables are independent of whether the photon goes with or against the rotation of the background, which is different with those in the usual four-dimensional Kerr black hole spacetime. Moreover, we also find that with the increase of the scale of extra dimension ?0, the marginally circular photon radius ? ps and the angular position of the relativistic images ? ? first decreases and then increases in the rotating squashed KK black hole for fixed rotation parameter b, but in the squashed KK G�del black hole they increase for the smaller global rotation parameter j and decrease for the larger one. In the extremely squashed case ? 0 = 0, the coefficient a in the rotating squashed KK black hole increases monotonously with the rotation parameter, but in the squashed KK G�del black hole it is a constant and independent of the global rotation of the G�del Universe. These information could help us to understand further the effects of the rotation parameter and the scale of extra dimension on the strong gravitational lensing in the black hole spacetimes.
Ji, Liyong; Chen, Songbai; Jing, Jiliang
Strong gravitational lensing across a dilaton anti-de Sitter black hole
In this work we investigate the gravitational lensing effect in the strong field region around dilaton black holes in an anti-de Sitter space. We also analyze the dependence of the radius of the photon sphere and deflection angle on dilaton coupling and the cosmological constant in this black hole spacetime. Finally the values of minimum impact parameter, the separation between the first and the other images, as well as the ratio between the flux of the first image and the flux coming from all the other images are determined to characterize some possible distinct signatures of such black holes.
Ghosh, Tanwi; SenGupta, Soumitra [Department of Theoretical Physics, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700 032 (India)
The Shear Testing Programme - I. Weak lensing analysis of simulated ground-based observations
NASA Astrophysics Data System (ADS)
The Shear Testing Programme (STEP) is a collaborative project to improve the accuracy and reliability of all weak lensing measurements in preparation for the next generation of wide-field surveys. In this first STEP paper, we present the results of a blind analysis of simulated ground-based observations of relatively simple galaxy morphologies. The most successful methods are shown to achieve percent level accuracy. From the cosmic shear pipelines that have been used to constrain cosmology, we find weak lensing shear measured to an accuracy that is within the statistical errors of current weak lensing analyses, with shear measurements accurate to better than 7 per cent. The dominant source of measurement error is shown to arise from calibration uncertainties where the measured shear is over or underestimated by a constant multiplicative factor. This is of concern as calibration errors cannot be detected through standard diagnostic tests. The measured calibration errors appear to result from stellar contamination, false object detection, the shear measurement method itself, selection bias and/or the use of biased weights. Additive systematics (false detections of shear) resulting from residual point-spread function anisotropy are, in most cases, reduced to below an equivalent shear of 0.001, an order of magnitude below cosmic shear distortions on the scales probed by current surveys. Our results provide a snapshot view of the accuracy of current ground-based weak lensing methods and a benchmark upon which we can improve. To this end we provide descriptions of each method tested and include details of the eight different implementations of the commonly used Kaiser, Squires & Broadhurst method (KSB+) to aid the improvement of future KSB+ analyses.
Heymans, Catherine; Van Waerbeke, Ludovic; Bacon, David; Berge, Joel; Bernstein, Gary; Bertin, Emmanuel; Bridle, Sarah; Brown, Michael L.; Clowe, Douglas; Dahle, H�kon; Erben, Thomas; Gray, Meghan; Hetterscheidt, Marco; Hoekstra, Henk; Hudelot, Patrick; Jarvis, Mike; Kuijken, Konrad; Margoniner, Vera; Massey, Richard; Mellier, Yannick; Nakajima, Reiko; Refregier, Alexandre; Rhodes, Jason; Schrabback, Tim; Wittman, David
Bayesian Galaxy Shape Measurement for Weak Lensing Surveys -I. Methodology and a Fast Fitting Algorithm
The principles of measuring the shapes of galaxies by a model-fitting\\u000aapproach are discussed in the context of shape-measurement for surveys of weak\\u000agravitational lensing. It is argued that such an approach should be optimal,\\u000aallowing measurement with maximal signal-to-noise, coupled with estimation of\\u000ameasurement errors. The distinction between likelihood-based and Bayesian\\u000amethods is discussed. Systematic biases in the Bayesian
L. Miller; T. D. Kitching; C. Heymans; A. F. Heavens; L. Van Waerbeke
Measuring Primordial Non-gaussianity Through Weak-lensing Peak Counts
NASA Astrophysics Data System (ADS)
We explore the possibility of detecting primordial non-Gaussianity of the local type using weak-lensing peak counts. We measure the peak abundance in sets of simulated weak-lensing maps corresponding to three models f NL = 0, - 100, and 100. Using survey specifications similar to those of EUCLID and without assuming any knowledge of the lens and source redshifts, we find the peak functions of the non-Gaussian models with f NL = �100 to differ by up to 15% from the Gaussian peak function at the high-mass end. For the assumed survey parameters, the probability of fitting an f NL = 0 peak function to the f NL = �100 peak functions is less than 0.1%. Assuming the other cosmological parameters are known, f NL can be measured with an error ?f NL ? 13. It is therefore possible that future weak-lensing surveys like EUCLID and LSST may detect primordial non-Gaussianity from the abundance of peak counts, and provide information complementary to that obtained from the cosmic microwave background.
Marian, Laura; Hilbert, Stefan; Smith, Robert E.; Schneider, Peter; Desjacques, Vincent
Wide-Field Weak Lensing by RX J1347-1145
NASA Astrophysics Data System (ADS)
We present an analysis of weak-lensing observations for RX J1347-1145 over a 43'�43' field taken in B and R filters on the Blanco 4 m telescope at CTIO. RX J1347-1145 is a massive cluster at redshift z=0.45. Using a population of galaxies with 20
Kling, Thomas P.; Dell'Antonio, Ian; Wittman, David; Tyson, J. Anthony
A technique for using radio jets as extended gravitational lensing probes
NASA Technical Reports Server (NTRS)
A new and potentially powerful method of measuring the mass of a galaxy (or dark matter concentration) which lies close in position to a background polarized radio jet is proposed. Using the fact that the polarization angle is not changed by lensing, an 'alignment-breaking parameter' is defined which is a sensitive indicator of gravitational distortion. The method remains sensitive over a wide redshift range of the gravitational lens. This technique is applied to the analysis of polarimetric observations of the jet of 3C 9 at z = 2.012, combined with a newly discovered 20.3 mag foreground galaxy at z = 0.2538 to 'weigh' the galaxy and obtain an approximate upper limit to the mass-to-light ratio.
Kronberg, Philipp P.; Dyer, Charles C.; Burbidge, E. Margaret; Junkkarinen, Vesa T.
Strong gravitational lensing in a black-hole spacetime dominated by dark energy
NASA Astrophysics Data System (ADS)
We study the influence of phantom fields on strong field gravitational lensing. Supposing that the gravitational field of the supermassive central object of the Galaxy is described by a phantom black hole metric, we estimate the numerical values of the coefficients and observations and find that the influence of the phantom fields is somewhat similar to that of the electric charge in a Reissner-Nordstr�m black hole, i.e., the deflect angle and angular separation increase with the phantom constant b. However, other observations are contrary to the Reissner-Nordstr�m case and show the effects of dark energy, such as (i) compressing the usual black hole and more powerfully attracting photons, (ii) making the relativistic Einstein ring larger than that of the usual black hole, and (iii) not weakening the usual relative magnitudes, which will facilitate observations.
Ding, Chikun; Liu, Changqing; Xiao, Yuanyuan; Jiang, Liqun; Cai, Rong-Gen
The design and alignment of the DECam lenses and modelling of the static shear pattern and its impact on weak lensing measurements
NASA Astrophysics Data System (ADS)
The Dark Energy Survey (DES) will produce high quality images covering over 5000 square degrees of the sky, with precise photometric redshifts between z = 0.2 to z = 1.3, using g, r, i, z and Y filters. The Dark Energy Camera (DECam), under construction for this survey, consists of wide field corrector optics and a CCD detector array that will give a 2.2 square degree field of view. It will be placed at the prime focus of the Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory in Chile. The Optical Science Laboratory (OSL) at University College London (UCL) is undertaking the alignment of the five lenses in the imaging system. These lenses range in diameter from 0.60 - 0.98 meters. The lenses must be held within tight tolerance limits in order to meet the DES science requirements. The tolerances are especially driven by the accuracy in the measurement of the weak lensing signal. This paper details the design for the cells that will hold the lenses and the alignment procedure for the mounting of the lenses and cells. Also presented is the expected static shear distortion pattern that will be generated and the impact of this pattern on the weak lensing signal measurement.
Antonik, M.; Doel, P.; Brooks, D.; Bridle, S.; Abbot, T.; Bernstein, R.; Bigelow, B.; Cease, H.; DePoy, D. L.; Flaugher, B.; Gladders, M.; Gutierrez, G.; Kent, S.; Stefanik, A.; Walker, A.; Worswick, S.
Weak-lensing Mass Measurements of Five Galaxy Clusters in the South Pole Telescope Survey Using Magellan/Megacam
NASA Astrophysics Data System (ADS)
We use weak gravitational lensing to measure the masses of five galaxy clusters selected from the South Pole Telescope (SPT) survey, with the primary goal of comparing these with the SPT Sunyaev-Zel'dovich (SZ) and X-ray-based mass estimates. The clusters span redshifts 0.28 < z < 0.43 and have masses M 500 > 2 � 1014 h -1 M ?, and three of the five clusters were discovered by the SPT survey. We observed the clusters in the g'r'i' passbands with the Megacam imager on the Magellan Clay 6.5 m telescope. We measure a mean ratio of weak-lensing (WL) aperture masses to inferred aperture masses from the SZ data, both within an aperture of R 500, SZ derived from the SZ mass, of 1.04 � 0.18. We measure a mean ratio of spherical WL masses evaluated at R 500, SZ to spherical SZ masses of 1.07 � 0.18, and a mean ratio of spherical WL masses evaluated at R 500, WL to spherical SZ masses of 1.10 � 0.24. We explore potential sources of systematic error in the mass comparisons and conclude that all are subdominant to the statistical uncertainty, with dominant terms being cluster concentration uncertainty and N-body simulation calibration bias. Expanding the sample of SPT clusters with WL observations has the potential to significantly improve the SPT cluster mass calibration and the resulting cosmological constraints from the SPT cluster survey. These are the first WL detections using Megacam on the Magellan Clay telescope.
High, F. W.; Hoekstra, H.; Leethochawalit, N.; de Haan, T.; Abramson, L.; Aird, K. A.; Armstrong, R.; Ashby, M. L. N.; Bautz, M.; Bayliss, M.; Bazin, G.; Benson, B. A.; Bleem, L. E.; Brodwin, M.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Clocchiatti, A.; Conroy, M.; Crawford, T. M.; Crites, A. T.; Desai, S.; Dobbs, M. A.; Dudley, J. P.; Foley, R. J.; Forman, W. R.; George, E. M.; Gladders, M. D.; Gonzalez, A. H.; Halverson, N. W.; Harrington, N. L.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hrubes, J. D.; Jones, C.; Joy, M.; Keisler, R.; Knox, L.; Lee, A. T.; Leitch, E. M.; Liu, J.; Lueker, M.; Luong-Van, D.; Mantz, A.; Marrone, D. P.; McDonald, M.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Mocanu, L.; Mohr, J. J.; Montroy, T. E.; Murray, S. S.; Natoli, T.; Nurgaliev, D.; Padin, S.; Plagge, T.; Pryke, C.; Reichardt, C. L.; Rest, A.; Ruel, J.; Ruhl, J. E.; Saliwanchik, B. R.; Saro, A.; Sayre, J. T.; Schaffer, K. K.; Shaw, L.; Schrabback, T.; Shirokoff, E.; Song, J.; Spieler, H. G.; Stalder, B.; Staniszewski, Z.; Stark, A. A.; Story, K.; Stubbs, C. W.; �uhada, R.; Tokarz, S.; van Engelen, A.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Williamson, R.; Zahn, O.; Zenteno, A.
The 400d Galaxy Cluster Survey weak lensing programme. I. MMT/Megacam analysis of CL0030+2618 at z = 0.50
NASA Astrophysics Data System (ADS)
Context. Studying cosmological structure formation provides insights into all of the universe's components: baryonic matter, dark matter, and, notably, dark energy. Measuring the mass function of galaxy clusters at high redshifts is particularly useful probe for both learning about the history of structure formation and constraining cosmological parameters. Aims: We attempt to derive reliable masses for a high-redshift, high-luminosity sample of galaxy clusters selected from the 400d X-ray selected cluster survey. Weak gravitational lensing allows us to determine masses that can be compared with those inferred from X-rays, forming an independent test. We focus on a particular object, CL0030+2618 at z = 0.50. Methods: Using deep imaging in three passbands acquired using the Megacam instrument at MMT, we show that Megacam is well-suited to measuring gravitational shear, i.e., the shapes of faint galaxies. A catalogue of background galaxies is constructed by analysing the photometric properties of galaxies in the g'r'i' bands. Results: Using the aperture mass technique, we detect the weak lensing signal of CL0030+2618 at 5.8? significance. We find significant tangential alignment of galaxies out to 10' or a distance of >2 r200 from the cluster centre. The weak lensing centre of CL0030+2618 agrees with several X-ray measurements and the position of the brightest cluster galaxy. Finally, we infer a weak lensing virial mass of M200 = 7.2+3.6+2.3-2.9-2.5 � 1014 {M}? for CL0030+2618. Conclusions: Despite complications caused by a tentative foreground galaxy group along the line of sight, the X-ray and weak lensing estimates for CL0030+2618 are in remarkable agreement. Observations reported here were obtained at the MMT Observatory, a joint facility of the Smithsonian Institution and the University of Arizona. Our MMT observations were supported in part by a donation from the F. H. Levinson Fund of the Silicon Valley Community Foundation to the University of Virginia. In addition, MMT observations used for this project were granted by the Smithsonian Astrophysical Observatory and by NOAO, through the Telescope System Instrumentation Program (TSIP). TSIP is funded by NSF.
Israel, H.; Erben, T.; Reiprich, T. H.; Vikhlinin, A.; Hildebrandt, H.; Hudson, D. S.; McLeod, B. A.; Sarazin, C. L.; Schneider, P.; Zhang, Y.-Y.
SDSS J131339.98+515128.3: A new GravitationallyLensed Quasar Selected Based on Near-infrared Excess
We report the discovery of a new gravitationally lensed quasar, SDSS J131339.98+515128.3, at a redshift of 1:875 with an image separation of 1: 0024. The lensing galaxy is clearly detected in visible-light follow-up observations. We also identify three absorption-line doublets in the spectra of the lensed quasar images, from which we measure the lens redshift to be 0:194. Like several other known lenses, the lensed quasar images have different continuum slopes. This difference is probably the result of reddening and microlensing in the lensing galaxy. The lensed quasar was selected by correlating Sloan Digital Sky Survey (SDSS) spectroscopic quasars with Two Micron All Sky Survey (2MASS) sources and choosing quasars that show near-infrared (IR) excess. The near-IR excess can originate, for example, from the contribution of the lensing galaxy at near-IR wavelengths. We show that the near-IR excess technique is indeed an efficient method to identify lensed systems from a large sample of quasars.
Ofek, E.O.; Oguri, M.; Jackson, N.; Inada, N.; Kayo, I.
Gravitational Lensing Of The Relativistic Jets As A Tool For The Study Their Structure And Estimations Of The Hubble Constant
NASA Astrophysics Data System (ADS)
Modeling the behavior of relativistic lets in gravitationally lensed systems was performed. We considered models with different distributions of the lens mass, in particular, a singular isothermal ellipsoid, an isothermal ellipsoid with a core, two- and three- component models with a galactic disk, halo, and bulge. We showed that the observed large-scale ring structures, which are observed in several sources, could be produced by the gravitational lensing of relativistic jets by galaxies for certain relative positions of the jet and the caustic curves. It was obtained estimations of the Hubble constant using the modeling observational data for the source B0218+357.
Larchenkova, T.; Lyskova, N.; Lutovinov, A.
Full-sky formulae for weak lensing power spectra from total angular momentum method
NASA Astrophysics Data System (ADS)
We systematically derive full-sky formulae for the weak lensing power spectra generated by scalar, vector and tensor perturbations from the total angular momentum (TAM) method. Based on both the geodesic and geodesic deviation equations, we first give the gauge-invariant expressions for the deflection angle and Jacobi map as observables of the CMB lensing and cosmic shear experiments. We then apply the TAM method, originally developed in the theoretical studies of CMB, to a systematic derivation of the angular power spectra. The TAM representation, which characterizes the total angular dependence of the spatial modes projected along a line-of-sight, can carry all the information of the lensing modes generated by scalar, vector, and tensor metric perturbations. This greatly simplifies the calculation, and we present a complete set of the full-sky formulae for angular power spectra in both the E-/B-mode cosmic shear and gradient-/curl-mode lensing potential of deflection angle. Based on the formulae, we give illustrative examples of non-vanishing B-mode cosmic shear and curl-mode of deflection angle in the presence of the vector and tensor perturbations, and explicitly compute the power spectra.
Yamauchi, Daisuke; Namikawa, Toshiya; Taruya, Atsushi
Formulating weak lensing from the Boltzmann equation and application to lens-lens couplings
NASA Astrophysics Data System (ADS)
The Planck mission has conclusively detected lensing of the cosmic microwave background (CMB) radiation from foreground sources to an overall significance of greater than 25? [1]. The high precision of this measurement motivates the development of a more complete formulation of the calculation of this effect. While most effects on the CMB anisotropies are widely studied through direct solutions of the Boltzmann equation, the nonlinear effect of CMB lensing is formulated through the solutions of the geodesic equation. In this paper, we present a new formalism to the calculation of the lensing effect by directly solving the Boltzmann equation, as we did in the calculation of the CMB anisotropies at recombination. In particular, we developed a diagrammatic approach to efficiently keep track of all the interaction terms and calculate all possible nontrivial correlations to arbitrary high orders. Using this formalism, we explicitly articulate the approximations required to recover the usual remapping approach used in current studies of the weak lensing. In addition, we point out additional unexplored corrections that are manifest in our formalism to which experiments may be sensitive. As an example, we calculate the correction to the CMB temperature power spectrum for the lens-lens coupling effects which are neglected in standard calculations. We find that the correction is ?0.1% of the CMB temperature power spectrum for ? up to 3000 and thus is comparable to the cosmic variance.
Su, S.-C.; Lim, Eugene A.
The Deltatheta-z_s relation for gravitational lenses as a cosmological test
NASA Astrophysics Data System (ADS)
Recently, Park & Gott claimed that there is a statistically significant, strong, negative correlation between the image separation Deltatheta and source redshift z_s for gravitational lenses. This is somewhat puzzling if one believes in a flat (k=0) universe, since in this case the typical image separation is expected to be independent of the source redshift, while one expects a negative correlation in a k=-1 universe and a positive one in a k=+1 universe. Park & Gott explored several effects that could cause the observed correlation, but no combination of these can explain the observations with a realistic scenario. Here, I explore this test further in three ways. First, I show that in an inhomogeneous universe a negative correlation is expected regardless of the value of k. Secondly, I test whether the Deltatheta-z_s relation can be used as a test to determine lambda_0 and Omega_0, rather than just the sign of k. Thirdly, I compare the results of the test from the Park & Gott sample with those using other samples of gravitational lenses, which can illuminate (unknown) selection effects and probe the usefulness of the Deltatheta-z_s relation as a cosmological test.
Helbig, Phillip
Statistical Properties of Gravitational Lensing in Cosmological Models with Cosmological Constant
NASA Astrophysics Data System (ADS)
To extend the work of Gott, Park, and Lee(1989), statistical properties of gravitational lensing in a wide variety of cosmological models involving non-zero cosmological constant is investigated, using the redshifts of both lens and source and observed angular separation of images for gravitational lens systems. We assume singular isothermal sphere as lensing galaxy in homogeneous and isotropic Friedmann-Lemaitre-Robertson-Walker universe, Schechter luminosity function, standard angular diameter distance formula and other galaxy parameters used in Fukugita and Turner(1991). To find the most adequate flat cosmological model and put a limit on the value of dimensionless cosmological constant lambda_o, the mean value of angular separation of images, probability distribution of angular separation and cumulative probability are calculated for given source and lens redshifts and compared with the observed values through several statistical methods. When there is no angular selection effect, models with highest value of lambda_o is preferred generally. When the angular selection effects are considered, the preferred model depends on the shape of selection functions and statistical methods; yet, models with large lambda_o are preferred in general. However, the present data cannot rule out any of the flat universe models with enough confidence. This approach can potentially select out best model. But at the moment, we need more data.
Lee, Hyun-A.; Park, Myeong-Gu
IRS Spectroscopy of Gravitationally Lensed z>1 Infrared-Luminous Galaxies
NASA Astrophysics Data System (ADS)
MIPS has detected 24um sources down to 50 uJy in well-studied fields (e.g., HDF-N, CDF-S), enabling us to study infrared galaxies out to z~3. Unfortunately, very little is known about the mid-infrared spectral properties of the ~<300 uJy sources that dominate the number counts, because IRS spectroscopy at these fluxes requires prohibitively expensive exposure times. Last cycle, we began solving this problem by targeting gravitationally lensed 24um sources behind lensing clusters. Their fluxes have been amplified by factors of 3--22. As a result, 1--2 hr integrations per LL setting produce high-quality spectra of sources with apparent flux densities of 500--1000 uJy, but intrinsic flux densities of only 30--250 uJy. To date, we have obtained spectra for 12 sources, showing a range of spectral properties (from PAHs to featureless continua). The goals are to characterize the spectral properties of the sources that dominate the 24um number counts (and how their spectra differ from low-redshift analogues); and test & recalibrate photometric redshift methods for faint 24um sources. These goals require the largest sample possible. Here, we propose IRS spectroscopy of 8 additional targets, newly identified from the MIPS GTO 24um images, and gravitationally amplified 3--10x. We can thus build up the sample necessary to characterize the nature of sources at 24um confusion limit.
Rieke, George; Egami, Eiichi; Fadda, Dario; Hines, Dean; Kneib, Jean-Paul; Marcillac, Delphine; Papovich, Casey; Richard, Johan; Rigby, Jane; Smith, Graham; Willmer, Christopher
The Amplitude of Mass Fluctuations and Mass Density of the Universe Constrained by Strong Gravitational Lensing
NASA Astrophysics Data System (ADS)
We investigate the linear amplitude of mass fluctuations in the universe, ?8, and the present mass density parameter of the Universe, ?m, from statistical strong gravitational lensing. We use the two population model of lens halos with fixed cooling mass scale Mc=3� 1013h-1M? to match the observed lensing probabilities, and leave ?8 or ?m as a free parameter to be constrained by the data. Another varying parameter, the equation of state of dark energy ?, and its typical values of -1, -2/3, -1/2 and -1/3 are investigated. We find that ?8 is degenerate with ?m in a way similar to that suggested by present day cluster abundance as well as cosmic shear lensing measurements: ?8?m0.6? 0.33. However, both ?8? 0.7 and ?m? 0.2 can be safely ruled out, the best fit is when ?8=1.0, ?m=0.3 and ?=- 1. This result is different from that obtained by Bahcall & Bode, who gave ?8 =0.98� 0.1 and ?m =0.17� 0.05. For ?8=1.0, the higher value of ?m=0.35 requires ?=-2/3 and ?m=0.40 requires ?=-1/2.
Chen, Da-Ming
Gravitational Lensing as Probe of Large Scale Structure of the Universe
NASA Astrophysics Data System (ADS)
Gravitational lenses are now recognized as important cosmological tools to probe the large scale structure of the universe. We use lensing statistics to constrain the cosmological parameter ??, to place limits on the average red-shift of gamma-ray bursters (GRBs), and to discriminate among the various models of galaxy evolution. We calculate the number of lenses formed in non-evolving model and in models in which galaxies evolve by fast or slow merging or by accreting matter from their surroundings. We find the value of ?? which is consistent with other estimates. We show that the upper limit on is higher in models in which galaxies are evolving. We calculate the distribution of lens image separation in various models of galaxy evolution and compare the results with the HST Snapshot Survey. We show that the Survey does not favour the fast merging models, while the mass accretion and non-evolving models may be able to explain the observed small angle separation.
Bhatia, V. B.; Jain, D.; Mahajan, S.; Panchapakesan, N.
Density Profile, Velocity Anisotropy, and Line-of-sight External Convergence of SLACS Gravitational Lenses
NASA Astrophysics Data System (ADS)
Data from 58 strong-lensing events surveyed by the Sloan Lens ACS Survey are used to estimate the projected galaxy mass inside their Einstein radii by two independent methods: stellar dynamics and strong gravitational lensing. We perform a joint analysis of these two estimates inside models with up to three degrees of freedom with respect to the lens density profile, stellar velocity anisotropy, and line-of-sight (LOS) external convergence, which incorporates the effect of the large-scale structure on strong lensing. A Bayesian analysis is employed to estimate the model parameters, evaluate their significance, and compare models. We find that the data favor Jaffe's light profile over Hernquist's, but that any particular choice between these two does not change the qualitative conclusions with respect to the features of the system that we investigate. The density profile is compatible with an isothermal, being sightly steeper and having an uncertainty in the logarithmic slope of the order of 5% in models that take into account a prior ignorance on anisotropy and external convergence. We identify a considerable degeneracy between the density profile slope and the anisotropy parameter, which largely increases the uncertainties in the estimates of these parameters, but we encounter no evidence in favor of an anisotropic velocity distribution on average for the whole sample. An LOS external convergence following a prior probability distribution given by cosmology has a small effect on the estimation of the lens density profile, but can increase the dispersion of its value by nearly 40%.
Guimar�es, Antonio C. C.; Sodr�, Laerte, Jr.
Weak lensing predictions for coupled dark energy cosmologies at non-linear scales
NASA Astrophysics Data System (ADS)
We present non-linear weak lensing predictions for coupled dark energy models using the Coupled Dark Energy Cosmological Simulations (CoDECS) simulations. We calculate the shear correlation function and error covariance expected for these models, for forthcoming ground-based [such as Dark Energy Survey (DES)] and space-based (Euclid) weak lensing surveys. We obtain predictions for the discriminatory power of a ground-based survey similar to DES and a space-based survey such as Euclid in distinguishing between ? cold dark matter (?CDM) and coupled dark energy models; we show that using the non-linear lensing signal we could discriminate between ?CDM and exponential constant coupling models with ?0? 0.1 at 4? confidence level with a DES-like survey and ?0? 0.05 at 5? confidence level with Euclid. We also demonstrate that estimating the coupled dark energy models' non-linear power spectrum, using the ?CDM HALOFIT fitting formula, results in biases in the shear correlation function that exceed the survey errors.
Beynon, Emma; Baldi, Marco; Bacon, David J.; Koyama, Kazuya; Sabiu, Cristiano
Cosmological constraints from the large-scale weak lensing of SDSS MaxBCG clusters
NASA Astrophysics Data System (ADS)
We derive constraints on the matter density ?m and the amplitude of matter clustering ?8 from measurements of large-scale weak lensing (projected separation R = 5-30 h-1 Mpc) by clusters in the Sloan Digital Sky Survey MaxBCG catalogue. The weak lensing signal is proportional to the product of ?m and the cluster-mass correlation function ?cm. With the relation between optical richness and cluster mass constrained by the observed cluster number counts, the predicted lensing signal increases with increasing ?m or ?8, with mild additional dependence on the assumed scatter between richness and mass. The dependence of the signal on scale and richness partly breaks the degeneracies among these parameters. We incorporate external priors on the richness-mass scatter from comparisons to X-ray data and on the shape of the matter power spectrum from galaxy clustering, and we test our adopted model for ?cm against N-body simulations. Using a Bayesian approach with minimal restrictive priors, we find ?8(?m/0.325)0.501 = 0.828 � 0.049, with marginalized constraints of ? _m=0.325_{-0.067}^{+0.086} and ? _8=0.828_{-0.097}^{+0.111}, consistent with constraints from other MaxBCG studies that use weak lensing measurements on small scales (R ? 2 h-1 Mpc). The (?m, ?8) constraint is consistent with and orthogonal to the one inferred from Wilkinson Microwave Anisotropy Probe cosmic microwave background data, reflecting agreement with the structure growth predicted by General Relativity for a ? cold dark matter (?CDM) cosmological model. A joint constraint assuming ?CDM yields ? _m=0.298_{-0.020}^{+0.019} and ? _8=0.831_{-0.020}^{+0.020}. For these parameters and our best-fitting scatter, we obtain a tightly constrained mean richness-mass relation of MaxBCG clusters, N200 = 25.4(M/3.61 � 1014 h-1 M?)0.74, with a normalization uncertainty of 1.5 per cent. Our cosmological parameter errors are dominated by the statistical uncertainties of the large-scale weak lensing measurements, which should shrink sharply with current and future imaging surveys.
Zu, Ying; Weinberg, David H.; Rozo, Eduardo; Sheldon, Erin S.; Tinker, Jeremy L.; Becker, Matthew R.
We present the analysis of the light curves of nine high-magnification single-lens gravitational microlensing events with lenses passing over source stars, including OGLE-2004-BLG-254, MOA-2007-BLG-176, MOA-2007-BLG-233/OGLE-2007-BLG-302, MOA-2009-BLG-174, MOA-2010-BLG-436, MOA-2011-BLG-093, MOA-2011-BLG-274, OGLE-2011-BLG-0990/MOA-2011-BLG-300, and OGLE-2011-BLG-1101/MOA-2011-BLG-325. For all of the events, we measure the linear limb-darkening coefficients of the surface brightness profile of source stars by measuring the deviation of the light curves near the peak affected by the finite-source effect. For seven events, we measure the Einstein radii and the lens-source relative proper motions. Among them, five events are found to have Einstein radii of less than 0.2 mas, making the lenses very low mass star or brown dwarf candidates. For MOA-2011-BLG-274, especially, the small Einstein radius of {theta}{sub E} {approx} 0.08 mas combined with the short timescale of t{sub E} {approx} 2.7 days suggests the possibility that the lens is a free-floating planet. For MOA-2009-BLG-174, we measure the lens parallax and thus uniquely determine the physical parameters of the lens. We also find that the measured lens mass of {approx}0.84 M{sub Sun} is consistent with that of a star blended with the source, suggesting that the blend is likely to be the lens. Although we did not find planetary signals for any of the events, we provide exclusion diagrams showing the confidence levels excluding the existence of a planet as a function of the separation and mass ratio.
Choi, J.-Y.; Shin, I.-G.; Park, S.-Y.; Han, C. [Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Gould, A.; Gaudi, B. S.; Henderson, C. B. [Department of Astronomy, Ohio State University, 140 W. 18th Ave., Columbus, OH 43210 (United States); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Beaulieu, J.-P. [Institut d'Astrophysique de Paris, UMR7095 CNRS-Universite Pierre and Marie Curie, 98 bis boulevard Arago, 75014 Paris (France); Street, R. [Las Cumbres Observatory Global Telescope Network, 6740B Cortona Dr, Suite 102, Goleta, CA 93117 (United States); Dominik, M. [School of Physics and Astronomy, SUPA, University of St. Andrews, North Haugh, St. Andrews, KY16 9SS (United Kingdom); Allen, W. [Vintage Lane Observatory, Blenheim (New Zealand); Almeida, L. A. [Instituto Nacional de Pesquisas Espaciais/MCTI, Sao Jose dos Campos, Sao Paulo (Brazil); Bos, M. [Molehill Astronomical Observatory, North Shore (New Zealand); Christie, G. W. [Auckland Observatory, P.O. Box 24-180, Auckland (New Zealand); Depoy, D. L. [Department of Physics, Texas A and M University, College Station, TX (United States); Dong, S. [Institute for Advanced Study, Einstein Drive, Princeton, NJ 08540 (United States); Drummond, J. [Possum Observatory, Patutahi (New Zealand); Gal-Yam, A. [Benoziyo Center for Astrophysics, Weizmann Institute (Israel); Collaboration: muFUN Collaboration; MOA Collaboration; OGLE Collaboration; PLANET Collaboration; RoboNet Collaboration; MiNDSTEp Consortium; and others
Constraints on early-type galaxy structure from spectroscopically selected gravitational lenses
NASA Astrophysics Data System (ADS)
This thesis describes all aspects of a unique spectroscopic survey for strong galaxy-galaxy gravitational lenses: motivation, candidate selection, ground- based spectroscopic follow-up, Hubble Space Telescope imaging, data analysis, and results on the radial density profile of the lens galaxies. The lens candidates are selected from within the spectroscopic database of the Sloan Digital Sky Survey (SDSS) based on the appearance of two significantly different redshifts along the same line of sight, and lenses are confirmed within the candidate sample by follow-up imaging and spectroscopy. The sample of [approximate]20 early-type lenses presented in this thesis represents the largest single strong-lens galaxy sample discovered and published to date. These lenses probe the mass of the lens galaxies on scales roughly equal to one-half effective radius. We find a dynamical normalization between isothermal lens-model velocity dispersions and aperture-corrected SDSS stellar velocity dispersions of f = s lens /s stars = 0.95 +/- 0.03. By combining lens-model Einstein radii and de Vaucouleurs effective radii with stellar velocity dispersions through the Jeans equation, we find that the logarithmic slope [Special characters omitted.] of the density profile in our lens galaxies (r 0 ( [Special characters omitted.] ) is on average slightly steeper than isothermal ([Special characters omitted.] = 2) with a modest intrinsic scatter. Parameterizing the intrinsic distribution in [Special characters omitted.] as Gaussian, we find a maximum-likelihood mean of [Special characters omitted. ] and standard deviation of s[Special characters omitted.] = [Special characters omitted.] (68% confidence, for isotropic velocity-dispersion models). Our results rule out a single universal logarithmic density slope at >99.995% confidence. The success of this spectroscopic lens survey suggests that similar projects should be considered as an explicit science goal of future redshift surveys. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.)
Bolton, Adam Stallard
Effects of dark matter substructures on gravitational lensing: results from the Aquarius simulations
NASA Astrophysics Data System (ADS)
We use the high-resolution Aquarius simulations of the formation of Milky Way-sized haloes in the ? cold dark matter cosmology to study the effects of dark matter substructures on gravitational lensing. Each halo is resolved with ~108 particles (at a mass resolution mp ~ 103 to 104h-1Msolar) within its virial radius. Subhaloes with masses msub >~ 105h-1Msolar are well resolved, an improvement of at least two orders of magnitude over previous lensing studies. We incorporate a baryonic component modelled as a Hernquist profile and account for the response of the dark matter via adiabatic contraction. We focus on the `anomalous' flux ratio problem, in particular on the violation of the cusp-caustic relation due to substructures. We find that subhaloes with masses less than ~108h-1Msolar play an important role in causing flux anomalies; such low-mass subhaloes have been unresolved in previous studies. There is large scatter in the predicted flux ratios between different haloes and between different projections of the same halo. In some cases, the frequency of predicted anomalous flux ratios is comparable to that observed for the radio lenses, although in most cases it is not. The probability for the simulations to reproduce the observed violations of the cusp lenses is ~10-3. We therefore conclude that the amount of substructure in the central regions of the Aquarius haloes is insufficient to explain the observed frequency of violations of the cusp-caustic relation. These conclusions are based purely on our dark matter simulations which ignore the effect of baryons on subhalo survivability.
Xu, D. D.; Mao, Shude; Wang, Jie; Springel, V.; Gao, Liang; White, S. D. M.; Frenk, Carlos S.; Jenkins, Adrian; Li, Guoliang; Navarro, Julio F.
A search for z= 7.3 Ly? emitters behind gravitationally lensing clusters
NASA Astrophysics Data System (ADS)
We searched for z= 7.3 Ly? emitters (LAEs) behind two gravitationally lensing clusters, Abell 2390 and CL 0024, using the Subaru Telescope Suprime-Cam and a narrow-band filter NB1006 (?c� 1005 nm and full width at half-maximum of about 21 nm). The combination of the fully depleted CCDs of the Suprime-Cam, sensitive to z� 7 Ly? emission at � 1 ?m, and the magnification by the lensing clusters can be potentially a powerful tool to detect faint distant LAEs. Using the NB1006 and deep optical to mid-infrared images of the clusters taken with the Hubble Space Telescope and Spitzer Space Telescope, we investigated if there exist objects consistent with the colour of z= 7.3 LAEs behind the clusters. We could not detect any LAEs to the unlensed Ly? line flux limit of FLy?? 6.9 � 10-18 erg s-1 cm-2. Using several z=7 Ly? luminosity functions (LFs) from the literature, we estimated and compared the expected detection numbers of z� 7$ LAEs in lensing and blank field surveys in the case of using an 8-m class ground-based telescope. Given the steep bright-end slope of the LFs, when the detector field of view (FOV) is comparable to the angular extent of a massive lensing cluster, imaging cluster(s) is (are) more efficient in detecting z� 7 LAEs than imaging a blank field. However, the gain is expected to be modest, a factor of 2 at most and likely much less depending on the adopted LFs. The main advantage of lensing survey, therefore, remains the gain in depth and not necessarily in detection efficiency. For much larger detectors, the lensing effect becomes negligible and the efficiency of LAE detection is proportional to the instrumental FOV. We also investigated the NB1006 images of the three z� 7 z-dropout galaxy candidates previously detected in Abell 2390 and found that none of them is detected in NB1006. Two of them are consistent with the predictions from previous studies that they would be at lower redshifts. The other one has a photometric redshift of z? 7.3, and if we assume that it is at z= 7.3, the unlensed Ly? line flux would be very faint: FLy? < 4.4 � 10-18 erg s-1 cm-2 (1? upper limit) or equivalent width of ? �. Its Ly? emission might be attenuated by neutral hydrogen, as recent studies show that the fraction of Lyman break galaxies displaying strong Ly? emission is lower at z� 7 than at z? 6.
Ota, Kazuaki; Richard, Johan; Iye, Masanori; Shibuya, Takatoshi; Egami, Eiichi; Kashikawa, Nobunari
We present a joint gravitational lensing and near-infrared study of the galaxy cluster Abell 3192 (A3192) that has been associated both with galaxies at z = 0.168 and with the X-ray luminous cluster RXC J0358.8-2955 (RXC J0358) at z = 0.425. Weak-lensing analysis of our Hubble Space Telescope snapshot observation with the Advanced Camera for Surveys detects two mass over-densities separated by {approx}2 arcmin, one adjacent to the optical position of A3192 (4.4{sigma} significance) and the other adjacent to the X-ray position of RXC J0358 (6.2{sigma} significance). These mass peaks coincide with peaks in the K-band luminosity density of galaxies with near-infrared colors consistent with the red sequence at z = 0.168 and z 0.425, respectively. Moreover, the Bayesian evidence of parameterized mass models that include two cluster/group-scale halos centered on the respective mass peaks exceeds that of single-halo models by a factor of {>=}10. The total projected mass of each galaxy system within 250 kpc of the respective peaks is M{sub WL}(z = 0.168) {approx_equal} 3 Multiplication-Sign 10{sup 13} M{sub Sun} and M{sub WL}(z = 0.425) {approx_equal} 1.2 Multiplication-Sign 10{sup 14} M{sub Sun }, both with total mass-to-light ratios of M{sub WL}/L{sub K} {approx_equal} 20 M{sub Sun }/L{sub Sun }. The original Abell cluster therefore comprises two independent galaxy systems-a foreground group at z = 0.168 and RXC J0358 at z = 0.425. Our results demonstrate the power of combining X-ray, near-infrared, and weak-lensing observations to select massive clusters, place those clusters and interloper galaxy systems along the line of sight, and measure their masses. This combination will be invaluable to robust interpretation of future high-redshift cluster surveys, including eROSITA.
Hamilton-Morris, Victoria; Smith, Graham P.; Haines, C. P.; Sanderson, A. J. R. [School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT (United Kingdom); Edge, A. C. [Institute of Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Egami, E. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Marshall, P. J. [Sub-department of Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Targett, T. A., E-mail: email@example.com, E-mail: firstname.lastname@example.com [SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh EH9 3HJ (United Kingdom)
PASCHEN-alpha EMISSION IN THE GRAVITATIONALLY LENSED GALAXY SMM J163554.2+661225
We report the detection of the Paalpha emission line in the z = 2.515 galaxy SMM J163554.2+661225 using Spitzer spectroscopy. SMM J163554.2+661225 is a submillimeter-selected infrared-luminous galaxy maintaining a high star formation rate (SFR), with no evidence of an active galactic nucleus from optical or infrared spectroscopy, nor X-ray emission. This galaxy is lensed gravitationally by the cluster Abell 2218, making it accessible to Spitzer spectroscopy. We measure a line luminosity, L(Paalpha) = (2.05 +- 0.33) x 10{sup 42} erg s{sup -1}, corrected for gravitational lensing. Comparing the Halpha and Paalpha luminosities, we derive a nebular extinction, A(V) = 3.6 +- 0.4 mag. The dust-corrected luminosity, L(Paalpha) = (2.57 +- 0.43) x 10{sup 42} erg s{sup -1}, corresponds to an ionization rate, Q {sub 0} = (1.6 +- 0.3) x 10{sup 55} gamma s{sup -1}. The instantaneous SFR is psi = 171 +- 28 M {sub sun} yr{sup -1}, assuming a Salpeter-like initial mass function from 0.1 to 100 M {sub sun} yr{sup -1}. The total IR luminosity derived using 70, 450, and 850 mum data is L{sub IR} = (5-10) x 10{sup 11} L {sub sun}, corrected for gravitational lensing. This corresponds to psi = 90-180 M {sub sun} yr{sup -1}, where the upper range is consistent with that derived from the Paalpha luminosity. While the L(8 mum)/L(Paalpha) ratio is consistent with the extrapolated relation observed in local galaxies and star-forming regions, the rest-frame 24 mum luminosity is significantly lower with respect to local galaxies of comparable Paalpha luminosity. Thus, SMM J163554.2+661225 arguably lacks a warmer dust component (T{sub D} approx 70 K), which is associated with deeply embedded star formation, and which contrasts with local galaxies with comparable SFRs. Rather, the starburst in SMM J163554.2+661225 is consistent with star-forming local galaxies with intrinsic luminosities, L{sub IR} approx 10{sup 10} L {sub sun}, but 'scaled up' by a factor of approx10-100.
Papovich, Casey; Finkelstein, Steven L. [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics, Texas A and M University, College Station, TX 77843-4242 (United States); Rudnick, Gregory [Department of Physics and Astronomy, 1251 Wescoe Hall Dr., University of Kansas, Lawrence, KS 66045-7582 (United States); Rigby, Jane R. [Observatories, Carnegie Institution of Washington, 813 Santa Barbara St., Pasadena, CA 91101 (United States); Willmer, Christopher N. A.; Egami, Eiichi; Rieke, Marcia [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Smith, J.-D. T., E-mail: firstname.lastname@example.com [Ritter Observatory, University of Toledo, MS 113, Toledo, OH 43606 (United States)
The stellar and dark matter distributions in elliptical galaxies from the ensemble of strong gravitational lenses
NASA Astrophysics Data System (ADS)
We derive the average mass profile of elliptical galaxies from the ensemble of 161 strong gravitational lens systems selected from several surveys, assuming that the mass profile scales with the stellar mass and effective radius of each lensing galaxy. The total mass profile is well fitted by a power law ?(r) ? r? with best-fitting slope ? = -2.11 � 0.05. The decomposition of the total mass profile into stellar and dark matter distributions is difficult due to a fundamental degeneracy between the stellar initial mass function (IMF) and the dark matter fraction fDM. We demonstrate that this IMF-fDM degeneracy can be broken by adding direct stellar mass fraction measurements by quasar microlensing observations. Our best-fitting model prefers the Salpeter IMF over the Chabrier IMF and a smaller central dark matter fraction than that predicted by adiabatic contraction models.
Oguri, Masamune; Rusu, Cristian E.; Falco, Emilio E.
Fermi LAT Observations of Gamma-ray Flaring in the Gravitationally Lensed Blazar B0218+357
NASA Astrophysics Data System (ADS)
Beginning mid-2012, increased gamma-ray activity from the radio double-imaged gravitationally lensed blazar B0218+357 was observed with the Fermi Large Area Telescope (LAT). The sustained flaring with daily fluxes greater than 10x the source's nominal level afforded an opportunity to uniquely measure the expected gravitational lens delay in gamma rays. Additionally, Fermi-LAT pointed observations of the anticipated delayed emission from the brightest flares with peaks ~60x its nominal flux at the end of September 2012 allowed us to constrain the magnification ratio between the images in gamma-rays. We will present the results from our timing and spectral analysis of B0218+357 and consider prospects for future LAT studies of gravitationally lensed systems.
Cheung, Chi (Teddy) C.; Scargle, J. D.; Corbet, R. H.; Fermi-LAT Collaboration
High-precision simulations of the weak lensing effect on cosmic microwave background polarization
NASA Astrophysics Data System (ADS)
We studied the accuracy, robustness, and self-consistency of pixel-domain simulations of the gravitational lensing effect on the primordial cosmic microwave background (CMB) anisotropies due to the large-scale structure of the Universe. In particular, we investigated the dependence of the precision of the results precision on some crucial parameters of these techniques and propose a semi-analytic framework to determine their values so that the required precision is a priori assured and the numerical workload simultaneously optimized. Our focus was on the B-mode signal, but we also discuss other CMB observables, such as the total intensity, T, and E-mode polarization, emphasizing differences and similarities between all these cases. Our semi-analytic considerations are backed up by extensive numerical results. Those are obtained using a code, nicknamed lenS2HAT - for lensing using scalable spherical harmonic transforms (S2HAT) - which we have developed in the course of this work. The code implements a version of the previously described pixel-domain approach and permits performing the simulations at very high resolutions and data volumes, thanks to its efficient parallelization provided by the S2HAT library - a parallel library for calculating of the spherical harmonic transforms. The code is made publicly available.
Fabbian, Giulio; Stompor, Radek
New Developments on Inverse Polygon Mapping to Calculate Gravitational Lensing Magnification Maps: Optimized Computations
NASA Astrophysics Data System (ADS)
We derive an exact solution (in the form of a series expansion) to compute gravitational lensing magnification maps. It is based on the backward gravitational lens mapping of a partition of the image plane in polygonal cells (inverse polygon mapping, IPM), not including critical points (except perhaps at the cell boundaries). The zeroth-order term of the series expansion leads to the method described by Mediavilla et al. The first-order term is used to study the error induced by the truncation of the series at zeroth order, explaining the high accuracy of the IPM even at this low order of approximation. Interpreting the Inverse Ray Shooting (IRS) method in terms of IPM, we explain the previously reported N -3/4 dependence of the IRS error with the number of collected rays per pixel. Cells intersected by critical curves (critical cells) transform to non-simply connected regions with topological pathologies like auto-overlapping or non-preservation of the boundary under the transformation. To define a non-critical partition, we use a linear approximation of the critical curve to divide each critical cell into two non-critical subcells. The optimal choice of the cell size depends basically on the curvature of the critical curves. For typical applications in which the pixel of the magnification map is a small fraction of the Einstein radius, a one-to-one relationship between the cell and pixel sizes in the absence of lensing guarantees both the consistence of the method and a very high accuracy. This prescription is simple but very conservative. We show that substantially larger cells can be used to obtain magnification maps with huge savings in computation time.
Mediavilla, E.; Mediavilla, T.; Mu�oz, J. A.; Ariza, O.; Lopez, P.; Gonzalez-Morcillo, C.; Jimenez-Vicente, J.
Interaction of a weak gravitational wave with a rotating magnetic dipole field
The interaction of a weak gravitational wave of specified frequency with a magnetic-dipole field rotating at a frequency much less than the gravitational-wave frequency is analyzed. The gravitational-wave source is assumed to be situated at the center of the magnetic dipole. It is shown that the interaction results in the production of an electromagnetic wave with the same frequency as
V. I. Denisov
An arbitrary surface mass density of the gravitational lens can be decomposed into multipole components. We simulate the ray tracing for the multipolar mass distribution of the generalized Singular Isothermal Sphere model based on deflection angles, which are analytically calculated. The magnification patterns in the source plane are then derived from an inverse shooting technique. As has been found, the caustics of odd mode lenses are composed of two overlapping layers for some lens models. When a point source traverses this kind of overlapping caustics, the image numbers change by {+-}4, rather than {+-}2. There are two kinds of caustic images. One is the critical curve and the other is the transition locus. It is found that the image number of the fold is exactly the average value of image numbers on two sides of the fold, while the image number of the cusp is equal to the smaller one. We also focus on the magnification patterns of the quadrupole (m = 2) lenses under the perturbations of m = 3, 4, and 5 mode components and found that one, two, and three butterfly or swallowtail singularities can be produced, respectively. With the increasing intensity of the high-order perturbations, the singularities grow up to bring sixfold image regions. If these perturbations are large enough to let two or three of the butterflies or swallowtails make contact, then eightfold or tenfold image regions can be produced as well. The possible astronomical applications are discussed.
Chu, Z.; Lin, W. P. [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Road, Shanghai 200030 (China); Li, G. L. [Purple Mountain Observatory, 2 West Beijing Road, Nanjing 210008 (China); Kang, X., E-mail: email@example.com, E-mail: email@example.com [Partner Group of MPI for Astronomy, Purple Mountain Observatory, 2 West Beijing Road, Nanjing 210008 (China)
Strong Gravitational Lensing as a Tool to Investigate the Structure of Jets at High Energies
NASA Astrophysics Data System (ADS)
The components of blazar jets that emit radiation span a factor of 1010 in scale. The spatial structure of these emitting regions depends on the observed energy. Photons emitted at different sites cross the lens plane at different distances from the mass-weighted center of the lens. Thus there are differences in magnification ratios and time delays between the images of lensed blazars observed at different energies. When the lens structure and redshift are known from optical observations, these constraints can elucidate the structure of the source at high energies. At these energies, current technology is inadequate to resolve these sources, and the observed light curve is thus the sum of the images. Durations of ?-ray flares are short compared with typical time delays; thus both the magnification ratio and the time delay can be measured for the delayed counterparts. These measurements are a basis for localizing the emitting region along the jet. To demonstrate the power of strong gravitational lensing, we build a toy model based on the best studied and the nearest relativistic jet M87.
Barnacka, Anna; Geller, Margaret J.; Dell'antonio, Ian P.; Benbow, Wystan
Weak Lensing Calibrated M-T Scaling Relation of Galaxy Groups in the COSMOS Fieldsstarf
NASA Astrophysics Data System (ADS)
The scaling between X-ray observables and mass for galaxy clusters and groups is instrumental for cluster-based cosmology and an important probe for the thermodynamics of the intracluster gas. We calibrate a scaling relation between the weak lensing mass and X-ray spectroscopic temperature for 10 galaxy groups in the COSMOS field, combined with 55 higher-mass clusters from the literature. The COSMOS data includes Hubble Space Telescope imaging and redshift measurements of 46 source galaxies per arcminute2, enabling us to perform unique weak lensing measurements of low-mass systems. Our sample extends the mass range of the lensing calibrated M-T relation an order of magnitude lower than any previous study, resulting in a power-law slope of 1.48^{+0.13}_{-0.09}. The slope is consistent with the self-similar model, predictions from simulations, and observations of clusters. However, X-ray observations relying on mass measurements derived under the assumption of hydrostatic equilibrium have indicated that masses at group scales are lower than expected. Both simulations and observations suggest that hydrostatic mass measurements can be biased low. Our external weak lensing masses provide the first observational support for hydrostatic mass bias at group level, showing an increasing bias with decreasing temperature and reaching a level of 30%-50% at 1 keV. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc., under NASA contract NAS 5-26555. Also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation; the National Radio Astronomy Observatory, which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.; and the Canada-France-Hawaii Telescope (CFHT) with MegaPrime/MegaCam operated as a joint project by the CFHT Corporation, CEA/DAPNIA, the National Research Council of Canada, the Canadian Astronomy Data Centre, the Centre National de la Recherche Scientifique de France, TERAPIX, and the University of Hawaii.
Kettula, K.; Finoguenov, A.; Massey, R.; Rhodes, J.; Hoekstra, H.; Taylor, J. E.; Spinelli, P. F.; Tanaka, M.; Ilbert, O.; Capak, P.; McCracken, H. J.; Koekemoer, A.
Mapping Dark Matter through Weak Lensing in the Extremely Overdense Aquarius and Microscopium Supercluster Cores
NASA Astrophysics Data System (ADS)
We propose deep imaging of intra-cluster regions near the cores of two extremely overdense superclusters (overdensity 50-100 in terms of average spatial density of rich clusters): the Aquarius supercluster (ASC) and the Microscopium supercluster (MSC), both located at ~ - 30�, for the purpose of mapping their dark matter distributions through weak lensing of sources behind them. These superclusters are similar in overdensity to the Corona Borealis supercluster (CSC). Our application of the Fundamental Plane (Batiste & Pearson, 2013) to the CSC suggests that there is collapse going on in the supercluster, whereas N-body analyses (Pearson & Batuski, 2013) indicate contrary results to that. The N-body analyses use only the masses within the clusters, which were shown to be insufficient to drive supercluster collapse, suggesting the presence of a yet undetected inter-cluster dark matter component. The ASC and MSC are similar objects to CSC. The DECam presents the perfect opportunity to trace the distribution of intra-cluster dark matter by imaging regions in our two supercluster cores (~ 3^� � 3?), with one field in each supercluster. Our analysis of the proposed photometry will map the distribution of dark matter through its weak lensing effects on sources behind our target supercluster cores.
Favia, Andrej; Batuski, David; Howell, Paul
Weak lensing effects in the measurement of the dark energy equation of state with LISA
The Laser Interferometer Space Antenna's (LISA's) observation of supermassive binary black holes (SMBBH) could provide a new tool for precision cosmography. Inclusion of subdominant signal harmonics in the inspiral signal allows for high-accuracy sky localization, dramatically improving the chances of finding the host galaxy and obtaining its redshift. A SMBBH merger can potentially have component masses from a wide range (10{sup 5}-10{sup 8}M{sub {center_dot}}) over which parameter accuracies vary considerably. We perform an in-depth study in order to understand (i) what fraction of possible SMBBH mergers allow for sky localization, depending on the parameters of the source, and (ii) how accurately w can be measured when the host galaxy can be identified. We also investigate how accuracies on all parameters improve when a knowledge of the sky position can be folded into the estimation of errors. We find that w can be measured to within a few percent in most cases, if the only error in measuring the luminosity distance is due to LISA's instrumental noise and the confusion background from Galactic binaries. However, weak lensing-induced errors will severely degrade the accuracy with which w can be obtained, emphasizing that methods to mitigate weak lensing effects would be required to take advantage of LISA's full potential.
Van Den Broeck, Chris [Nikhef, National Institute for Subatomic Physics, Science Park 105, 1098 XG Amsterdam (Netherlands); School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom); Trias, M.; Sintes, A. M. [Departament de Fisica, Universitat de les Illes Balears, Carretera Valldemossa Km. 7.5, E-07122 Palma de Mallorca (Spain); Sathyaprakash, B. S. [School of Physics and Astronomy, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA (United Kingdom)
The Time Delay in the Double Quasar 0957+561 and a Search for Gravitational Lenses
NASA Astrophysics Data System (ADS)
The flux densities of 0957+561 A and B have been monitored for the past eleven years using the VLA at lambda6 cm. The VLA data are best fit by a time delay of 1.40 +/- 0.1 yr (513 +/- 40 days) with the A image leading. Using recent estimates of the velocity dispersion in the principal lensing galaxy and the model of Falco, Gorenstein & Shapiro, an estimate of Hubble's constant can be obtained which falls between 46 and 90 km s^{-1} Mpc^{-1}. This result is an independent confirmation of the current determinations. The VLA data also show that the image magnification ratio changes substantially over the 50 milliarcsecond radio structure. The variable core flux has a magnification ratio of 0.765 +/- 0.052, in agreement with previous determinations from optical spectral line emission, and consistent with VLBI observations of the core flux variability. The nonvarying jet flux ratio is more difficult to determine from the VLA light curves, but appears to be consistent with the VLBI determinations of the jet flux ratio. The first two sessions of the MIT-Greenbank-VLA gravitational lens search at lambda3.6 cm have been completed. Over 100 candidates for gravitational lensing were identified on a morphological basis, of which 27 are particularly suggestive. This result gives encouragement to the continuing MG-VLA lambda3.6 cm lens search. Two candidates are particularly promising: MG0959+2947, a close pair of quasars at differing redshifts; and MG1549+3047, the fourth "Einstein ring" candidate to have been found. Using a point-mass model for the lensing galaxy, the mass-to-light ratio within the ring must exceed 8M_odot/L_odot, and the predicted central velocity dispersion is 180 km s^{-1}. These figures are typical for elliptical galaxies. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253-1690.).
Lehar, Joseph
Wave propagation in a weak gravitational field and the validity of the thin lens approximation
Wave effects can be important for the gravitational lensing of gravitational waves. In such a case, wave optics must be used instead of geometric optics. We consider a plane wave entering a lens object and solve numerically the wave equation for three lens models: the uniform density sphere, the singular isothermal sphere, and the Hernquist model. By comparing our numerical solutions with the analytical solutions under the thin lens approximation, we evaluate the error of this approximation. The results show that the relative error of the thin lens approximation is small if the geometrical thickness of the lens is much smaller than the distance between the lens and the observer.
Suyama, Teruaki; Michikoshi, Shugo [Department of Physics, Kyoto University, Kyoto 606-8502 (Japan); Takahashi, Ryuichi [Division of Theoretical Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan)
Statistics of mass substructure from strong gravitational lensing: quantifying the mass fraction and mass function
NASA Astrophysics Data System (ADS)
A Bayesian statistical formalism is developed to quantify the level at which the mass function (dN/dm ~ m-?) and the projected cumulative mass fraction (f) of [cold dark matter (CDM)] substructure in strong gravitational lens galaxies, with arcs or Einstein rings, can be recovered as function of the lens survey parameters and the detection threshold of the substructure mass. The method is applied to different sets of mock data to explore a range of observational limits: (i) the number of lens galaxies in the survey; (ii) the mass threshold, Mlow, for the detection of substructures and (iii) the uncertainty of the measured substructure masses. We explore two different priors on the mass function slope: a uniform prior and a Gaussian prior with ? = 1.90 +/- 0.1. With a substructure detection threshold Mlow = 3 � 108Msolar, the number of lenses available now (nl = 30), a true dark matter mass fraction in (CDM) substructure <=1.0 per cent and a prior of ? = 1.90 +/- 0.1, we find that the upper limit of f can be constrained down to a level <=1.0 per cent [95 per cent confidence level (CL)]. In the case of a uniform prior, the complete substructure mass distribution (i.e. mass fraction and slope) can only be characterized in a number of favourable cases with a large number of detected substructures. This can be achieved by an increase of the resolution and the signal-to-noise ratio of the lensed images. In the case of a Gaussian prior on ?, instead, it is always possible to set stringent constraints on both parameters. We also find that lowering the detection threshold has the largest impact on the ability to recover ?, because of the (expected) steep mass function slope. In the future, thanks to new surveys with telescopes, such as Square Kilometre Array (SKA), Large Synoptic Survey Telescope (LSST) and Joint Dark Energy Mission (JDEM) and follow-up telescopes with high-fidelity data, a significant increase in the number of known lenses (i.e. >>104) will allow us to recover the satellite population in its completeness. For example, a sample of 200 lenses, equivalent in data quality to the Sloan Lens ACS Survey and a detection threshold of 108Msolar, allows one to determine f = 0.5 +/- 0.1 per cent (68 per cent CL) and ? = 1.90 +/- 0.2 (68 per cent CL).
Vegetti, Simona; Koopmans, L. V. E.
Lensing reconstruction with CMB temperature and polarization
NASA Astrophysics Data System (ADS)
Weak gravitational lensing by an intervening large-scale structure induces a distinct signature in the cosmic microwave background (CMB) that can be used to reconstruct the weak-lensing displacement map. Estimators for individual Fourier modes of this map can be combined to produce an estimator for the lensing-potential power spectrum. The naive estimator for this quantity will be biased upwards by the uncertainty associated with reconstructing individual modes; we present an iterative scheme for removing this bias. The variance and covariance of the lensing-potential power spectrum estimator are calculated and evaluated numerically in a ?CDM universe for Planck and future polarization-sensitive CMB experiments.
Kesden, Michael; Cooray, Asantha; Kamionkowski, Marc
Discovery of a Gravitationally Lensed Quasar from theSloan Digital Sky Survey: SDSS J133222.62+034739.9
We report the discovery of the two-image gravitationally lensed quasar SDSS J133222.62+034739.9 (SDSS J1332+0347) with an image separation of {Delta}{theta} = 1.14''. This system consists of a source quasar at z{sub s} = 1.445 and a lens galaxy at z{sub l} = 0.191. The agreement of the luminosity, ellipticity and position angle of the lens galaxy with those expected from lens model confirms the lensing hypothesis.
Morokuma, Tomoki; Inada, Naohisa; Oguri, Masamune; Ichikawa, Shin-Ichi; Kawano, Yozo; Tokita, Kouichi; Kayo, Issha; Hall, Patrick B.; Kochanek, Christopher S.; Richards, Gordon T.; York, Donald G.; Schneider, Donald P.; /Tokyo U., Inst. Astron. /KIPAC, Menlo Park /Princeton U. /Tokyo, Astron. Observ. /Nagoya U. /York U., Canada /Ohio State U., Dept. Astron. /Johns Hopkins U. /Drexel U. /Chicago U., Astron. Astrophys. Ctr. /Chicago U., EFI /Penn State U., Astron. Astrophys.
We compare the efficiency of weak-lensing-selected galaxy cluster counts and of the weak-lensing bispectrum at capturing non-Gaussian features in the dark matter distribution. We use the halo model to compute the weak-lensing power spectrum, the bispectrum, and the expected number of detected clusters, and derive constraints on cosmological parameters for a large, low systematic weak-lensing survey, by focusing on the OMEGA{sub m}-sigma{sub 8} plane and on the dark energy equation of state. We separate the power spectrum into the resolved and the unresolved parts of the data, the resolved part being defined as detected clusters, and the unresolved part as the rest of the field. We consider four kinds of clusters counts, taking into account different amount of information: signal-to-noise ratio peak counts, counts as a function of clusters' mass, counts as a function of clusters' redshift, and counts as a function of clusters' mass and redshift. We show that when combined with the power spectrum, those four kinds of counts provide similar constraints, thus allowing one to perform the most direct counts, signal-to-noise peak counts, and get percent level constraints on cosmological parameters. We show that the weak-lensing bispectrum gives constraints comparable to those given by the power spectrum and captures non-Gaussian features as well as cluster counts, its combination with the power spectrum giving errors on cosmological parameters that are similar to, if not marginally smaller than, those obtained when combining the power spectrum with cluster counts. We finally note that in order to reach its potential, the weak-lensing bispectrum must be computed using all triangle configurations, as equilateral triangles alone do not provide useful information. The appendices summarize the halo model, and the way the power spectrum and bispectrum are computed in this framework.
Berge, Joel [Jet Propulsion Laboratory/California Institute of Technology, 4800 Oak Grove Drive, MS 169-327, Pasadena, CA 91109 (United States); Amara, Adam [Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 16, CH-8093 Zurich (Switzerland); Refregier, Alexandre, E-mail: email@example.com [Laboratoire AIM, CEA/DSM, CNRS, Universite Paris Diderot, DAPNIA/SAp, 91191 Gif-sur-Yvette (France)
A numerical study of the effects of primordial non-Gaussianities on weak lensing statistics
NASA Astrophysics Data System (ADS)
While usually cosmological initial conditions are assumed to be Gaussian, inflationary theories can predict a certain amount of primordial non-Gaussianity which can have an impact on the statistical properties of the lensing observables. In order to evaluate this effect, we build a large set of realistic maps of different lensing quantities starting from light cones extracted from large dark matter only N-body simulations with initial conditions corresponding to different levels of primordial local non-Gaussianity strength fNL. Considering various statistical quantities (probability distribution function, power spectrum, shear in aperture, skewness and bispectrum), we find that the effect produced by the presence of primordial non-Gaussianity is relatively small, being of the order of few per cent for values of | fNL| compatible with the present cosmic microwave background constraints and reaching at most 10-15 per cent for the most extreme cases with |fNL| = 1000. We also discuss the degeneracy of this effect with the uncertainties due to the power spectrum normalization ?8 and matter density parameter ?m, finding that an error in the determination of ?8 (?m) of about 3 (10) per cent gives differences comparable with non-Gaussian models having fNL=�1000. These results suggest that the possible presence of an amount of primordial non-Gaussianity corresponding to |fNL| = 100 is not hampering a robust determination of the main cosmological parameters in present and future weak lensing surveys, while a positive detection of deviations from the Gaussian hypothesis is possible only by breaking the degeneracy with other cosmological parameters and using data from deep surveys covering a large fraction of the sky.
Pace, F.; Moscardini, L.; Bartelmann, M.; Branchini, E.; Dolag, K.; Grossi, M.; Matarrese, S.
Atmospheric turbulence can mimic the effects of weak lensing in astronomical images, so it is necessary to understand to what degree turbulence affects weak lensing measurements. In particular, we studied the ellipticity induced upon the point-spread functions (PSFs) of a grid of simulated stars separated by distances (d {approx} 1{prime}) that will be characteristic of Large Synoptic Survey Telescope (LSST) images. We observe that atmospherically induced ellipticity changes on small scales (d < 0.5{prime}) and use linear interpolation between stars separated by d = 0.5{prime} to determine the induced ellipticity everywhere in the field-of-view.
Schlaufman, K
Mask Effects on Cosmological Studies with Weak-lensing Peak Statistics
NASA Astrophysics Data System (ADS)
With numerical simulations, we analyze in detail how the bad data removal, i.e., the mask effect, can influence the peak statistics of the weak-lensing convergence field reconstructed from the shear measurement of background galaxies. It is found that high peak fractions are systematically enhanced because of the presence of masks; the larger the masked area is, the higher the enhancement is. In the case where the total masked area is about 13% of the survey area, the fraction of peaks with signal-to-noise ratio ? >= 3 is ~11% of the total number of peaks, compared with ~7% of the mask-free case in our considered cosmological model. This can have significant effects on cosmological studies with weak-lensing convergence peak statistics, inducing a large bias in the parameter constraints if the effects are not taken into account properly. Even for a survey area of 9 deg2, the bias in (? m , ?8) is already intolerably large and close to 3?. It is noted that most of the affected peaks are close to the masked regions. Therefore, excluding peaks in those regions in the peak statistics can reduce the bias effect but at the expense of losing usable survey areas. Further investigations find that the enhancement of the number of high peaks around the masked regions can be largely attributed to the smaller number of galaxies usable in the weak-lensing convergence reconstruction, leading to higher noise than that of the areas away from the masks. We thus develop a model in which we exclude only those very large masks with radius larger than 3' but keep all the other masked regions in peak counting statistics. For the remaining part, we treat the areas close to and away from the masked regions separately with different noise levels. It is shown that this two-noise-level model can account for the mask effect on peak statistics very well, and the bias in cosmological parameters is significantly reduced if this model is applied in the parameter fitting.
Liu, Xiangkun; Wang, Qiao; Pan, Chuzhong; Fan, Zuhui
Weak lensing mass map and peak statistics in Canada-France-Hawaii Telescope Stripe 82 survey
NASA Astrophysics Data System (ADS)
We present a weak lensing mass map covering �124 deg2 of the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82). We study the statistics of rare peaks in the map, including peak abundance, the peak-peak correlation functions and the tangential-shear profiles around peaks. We find that the abundance of peaks detected in CS82 is consistent with predictions from a ? cold dark matter cosmological model, once noise effects are properly included. The correlation functions of peaks with different signal-to-noise ratio (SNR) are well described by power laws, and there is a clear cross-correlation between the Sloan Digital Sky Survey III/Constant Mass galaxies and high SNR peaks. The tangential-shear profiles around peaks increase with peak SNR. We fit analytical models to the tangential-shear profiles, including a projected singular isothermal sphere (SIS) model and a projected Navarro, Frenk & White (NFW) model, plus a two-halo term. For the high SNR peaks, the SIS model is rejected at �3?. The NFW model plus a two-halo term gives more acceptable fits to the data. Some peaks match the positions of optically detected clusters, while others are relatively dark. Comparing dark and matched peaks, we find a difference in lensing signal of a factor of 2, suggesting that about half of the dark peaks are false detections.
Shan, Huan Yuan; Kneib, Jean-Paul; Comparat, Johan; Jullo, Eric; Charbonnier, Ald�e; Erben, Thomas; Makler, Martin; Moraes, Bruno; Van Waerbeke, Ludovic; Courbin, Fr�d�ric; Meylan, Georges; Tao, Charling; Taylor, James E.
Weak-lensing detection of intracluster filaments with ground-based data
NASA Astrophysics Data System (ADS)
According to the current standard model of cosmology, matter in the Universe arranges itself along a network of filamentary structure. These filaments connect the main nodes of this so-called "cosmic web", which are clusters of galaxies. Although its large-scale distribution is clearly characterized by numerical simulations, constraining the dark-matter content of the cosmic web in reality turns out to be difficult. The natural method of choice is gravitational lensing. However, the direct detection and mapping of the elusive filament signal is challenging and in this work we present two methods that are specifically tailored to achieve this task. A linear matched filter aims at detecting the smooth mass-component of filaments and is optimized to perform a shear decomposition that follows the anisotropic component of the lensing signal. Filaments clearly inherit this property due to their morphology. At the same time, the contamination arising from the central massive cluster is controlled in a natural way. The filament 1? detection is of about ? ~ 0.01 - 0.005 according to the filter's template width and length, enabling the detection of structures beyond reach with other approaches. The second, complementary method seeks to detect the clumpy component of filaments. The detection is determined by the number density of subclump identifications in an area enclosing the potential filament, as was found within the observed field with the filter approach. We tested both methods against mocked observations based on realistic N-body simulations of filamentary structure and proved the feasibility of detecting filaments with ground-based data.
Maturi, Matteo; Merten, Julian
The signature of substructure on gravitational lensing in the ?CDM cosmological model
NASA Astrophysics Data System (ADS)
We present a study of the lens properties of quadruply imaged systems, lensed by numerically simulated galaxies. We investigate a simulated elliptical and disc galaxy drawn from high resolution simulations of galaxy formation in a concordance ?CDM universe. The simulations include the effects of gas dynamics, star formation and feedback processes. Flux-ratio anomalies observed in strong gravitational lensing potentially provide an indicator for the presence of mass substructure in lens galaxies as predicted from CDM simulations. We particularly concentrate on the prediction that, for an ideal cusp caustic, the sum of the signed magnifications of the three highly magnified images should vanish when the source approaches the cusp. Strong violation of this cusp relation indicates the presence of substructure, regardless of the global, smooth mass model of the lens galaxy. We draw the following conclusions: (1) the level of substructure present in simulations produces violations of the cusp relation comparable to those observed; (2) higher-order catastrophes (e.g. swallowtails) can also cause changes of the order of 0.6 in the cusp relation as predicted by a smooth model; (3) the flux anomaly distribution depends on the image parity and flux and both the brightest minimum and saddle-point images are more affected by substructure than the fainter images. In addition, the brightest saddle point is demagnified w.r.t. the brightest minimum. Our results are fully numerical and properly include all mass scales, without making semi-analytic assumptions. They are ultimately limited by the mass resolution of single particles in the simulation determined by current computational limits, however show that our results are not affected by shot-noise due to the finite number of particles.
Brada?, M.; Schneider, P.; Lombardi, M.; Steinmetz, M.; Koopmans, L. V. E.; Navarro, J. F.
Stochastic bias of colour-selected BAO tracers by joint clustering-weak lensing analysis
NASA Astrophysics Data System (ADS)
The baryon acoustic oscillation (BAO) feature in the two-point correlation function of galaxies supplies a standard ruler to probe the expansion history of the Universe. We study here several galaxy selection schemes, aiming at building an emission-line galaxy (ELG) sample in the redshift range 0.6 < z < 1.7, that would be suitable for future BAO studies, providing a highly biased galaxy sample. We analyse the angular galaxy clustering of galaxy selections at the redshifts 0.5, 0.7, 0.8, 1 and 1.2 and we combine this analysis with a halo occupation distribution (HOD) model to derive the properties of the haloes these galaxies inhabit, in particular the galaxy bias on large scales. We also perform a weak lensing analysis (aperture statistics) to extract the galaxy bias and the cross-correlation coefficient and compare to the HOD prediction. We apply this analysis on a data set composed of the photometry of the deep co-addition on Sloan Digital Sky Survey (SDSS) Stripe 82 (225 deg2), of Canada-France-Hawaii Telescope/Stripe 82 deep i-band weak lensing survey and of the Wide-Field Infrared Survey Explorer infrared photometric band W1. The analysis on the SDSS-III/constant mass galaxies selection at z = 0.5 is in agreement with previous studies on the tracer, moreover we measure its cross-correlation coefficient r = 1.16 � 0.35. For the higher redshift bins, we confirm the trends that the brightest galaxy populations selected are strongly biased (b > 1.5), but we are limited by current data sets depth to derive precise values of the galaxy bias. A survey using such tracers of the mass field will guarantee a high significance detection of the BAO.
Comparat, Johan; Jullo, Eric; Kneib, Jean-Paul; Schimd, Carlo; Shan, HuanYuan; Erben, Thomas; Ilbert, Olivier; Brownstein, Joel; Ealet, Anne; Escoffier, Stephanie; Moraes, Bruno; Mostek, Nick; Newman, Jeffrey A.; Pereira, M. E. S.; Prada, Francisco; Schlegel, David J.; Schneider, Donald P.; Brandt, Carlos H.
The Complex, Gravitationally Lensed Arc System in the X-Ray--selected Cluster of Galaxies MS 0440+0204
We report the discovery of a new, complex, gravitationally lensed arc system in the X-ray luminous cluster of galaxies MS 0440+0204 at z = 0.190. This cluster has Lx = 4.0 � 1044 ergs s-1 and is one of a sample of 38 high X-ray luminosity (Lx > 2 � 1044 ergs s-1), intermediate-redshift (z > 0.15) clusters we are
G. A. Luppino; I. M. Gioia; J. Annis; O. Le Fevre; F. Hammer
TESTING GRAVITATIONAL LENSING AS THE SOURCE OF ENHANCED STRONG Mg II ABSORPTION TOWARD GAMMA-RAY BURSTS
Sixty percent of gamma-ray bursts (GRBs) reveal strong Mg II absorbing systems, which is a factor of {approx}2 times the rate seen along lines of sight to quasars. Previous studies argue that the discrepancy in the strong Mg II covering factor is most likely to be the result of either quasars being obscured due to dust or the consequence of many GRBs being strongly gravitationally lensed. We analyze observations of quasars that show strong foreground Mg II absorption. We find that GRB lines of sight pass closer to bright galaxies than would be expected for random lines of sight within the impact parameter expected for strong Mg II absorption. While this cannot be explained by obscuration in the GRB sample, it is a natural consequence of gravitational lensing. Upon examining the particular configurations of galaxies near a sample of GRBs with strong Mg II absorption, we find several intriguing lensing candidates. Our results suggest that lensing provides a viable contribution to the observed enhancement of strong Mg II absorption along lines of sight to GRBs, and we outline the future observations required to test this hypothesis conclusively.
Rapoport, Sharon; Onken, Christopher A.; Schmidt, Brian P.; Tucker, Brad E. [Research School of Astronomy and Astrophysics, Australian National University, Weston Creek, ACT 2611 (Australia); Wyithe, J. Stuart B. [School of Physics, University of Melbourne, Parkville, Victoria 3010 (Australia); Levan, Andrew J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom)
The Generation of Gravitational Waves. 1. Weak-Field Sources: A Plug-in-and-Grind Formalism.
National Technical Information Service (NTIS)
A plug-in-and-grind formalism is derived for calculating the gravitational waves emitted by any system with weak internal gravitational fields. If the internal fields have negligible influence on the system's motions, then the formalism reduces to standar...
K. S. Thorne S. J. Kovacs
Reconstruction of the One-Point Distribution of Convergence from Weak Lensing by Large-Scale Structure
Weak-lensing measurements are starting to provide statistical maps of the distribution of matter in the universe that are increasingly precise and complementary to cosmic microwave background maps. The probability distribution function (PDF) provides a powerful tool to test non-Gaussian features in the convergence field and to discriminate the different cosmological models. In this paper, we present a new PDF space
Tong-Jie Zhang; Ue-Li Pen
S�rsic galaxy models in weak lensing shape measurement: model bias, noise bias and their interaction
NASA Astrophysics Data System (ADS)
Cosmic shear is a powerful probe of cosmological parameters, but its potential can be fully utilized only if galaxy shapes are measured with great accuracy. Two major effects have been identified which are likely to account for most of the bias seen for maximum likelihood methods in recent shear measurement challenges. Model bias occurs when the true galaxy shape is not well represented by the fitted model. Noise bias occurs due to the non-linear relationship between image pixels and galaxy shape. In this paper we investigate the potential interplay between these two effects when an imperfect model is used in the presence of high noise. We present analytical expressions for this bias, which depends on the residual difference between the model and real data. They can lead to biases not accounted for in previous calibration schemes. By measuring the model bias, noise bias and their interaction, we provide a complete statistical framework for measuring galaxy shapes with model fitting methods from GRavitational lEnsing Accuracy Testing (GREAT)-like images. We demonstrate the noise and model interaction bias using a simple toy model, which indicates that this effect can potentially be significant. Using real galaxy images from the Cosmological Evolution Survey (COSMOS) we quantify the strength of the model bias, noise bias and their interaction. We find that the interaction term is often of a similar size to the model bias term, and is smaller than the requirements of current and near future galaxy surveys.
Kacprzak, Tomasz; Bridle, Sarah; Rowe, Barnaby; Voigt, Lisa; Zuntz, Joe; Hirsch, Michael; MacCrann, Niall
Constraints on Cosmic Equation of State Using Gravitational Lensing Statistics with Evolving Galaxies
NASA Astrophysics Data System (ADS)
In this paper, observational constraints on the cosmic equation of state of dark energy (p = w ?) have been investigated using gravitational lensing statistics. A likelihood analysis of the lens survey has been carried out to constrain the cosmological parameters ?m and w. Constraints on ?m and w are obtained in three different models of galaxy evolution: no evolution model (comoving number density of galaxies remain constant), Volmerange and Guiderdoni Model and fast merging model. The last two models consider the number evolution of galaxies in addition to the luminosity evolution. The likelihood analysis shows that for the no-evolution case w <= -0.04 and ?m <= 0.90 at 1? (68% confidence level (CL)). Similarly for the Volmerange & Guiderdoni Model the constraints are w <= -0.04 and ?m <= 0.91 at 1?. In fast merging model the constraint become weaker and it allows almost the entire range of parameters. For the case of constant ? (w = -1), all the models permit ?m = 0.3 with 68% CL, which is consistent with the value of ?m inferred from various other cosmological observations.
Dev, Abha; Jain, Deepak; Panchapakesan, N.; Mahajan, S.; Bhatia, V. B.
THE REMARKABLE {gamma}-RAY ACTIVITY IN THE GRAVITATIONALLY LENSED BLAZAR PKS 1830-211
We report the extraordinary {gamma}-ray activity (E > 100 MeV) of the gravitationally lensed blazar PKS 1830-211 (z = 2.507) detected by AGILE between 2010 October and November. On October 14, the source experienced a factor of {approx}12 flux increase with respect to its average value and remained brightest at this flux level ({approx}500 x 10{sup -8} photons cm{sup -2} s{sup -1}) for about four days. The one-month {gamma}-ray light curve across the flare showed a mean flux F(E > 100 MeV) = 200 x 10{sup -8} photons cm{sup -2} s{sup -1}, which resulted in a factor of four enhancement with respect to the average value. Following the {gamma}-ray flare, the source was observed in near-IR (NIR)-optical energy bands at the Cerro Tololo Inter-American Observatory and in X-Rays by Swift/X-Ray Telescope and INTEGRAL/IBIS. The main result of these multifrequency observations is that the large variability observed in {gamma}-rays does not have a significant counterpart at lower frequencies: no variation greater than a factor of {approx}1.5 appeared in the NIR and X-Ray energy bands. PKS 1830-211 is then a good '{gamma}-ray only flaring' blazar showing substantial variability only above 10-100 MeV. We discuss the theoretical implications of our findings.
Donnarumma, I.; De Rosa, A.; Vittorini, V.; Tavani, M.; Striani, E.; Pacciani, L. [INAF/IASF-Roma, Via del Fosso del Cavaliere 100, I-00133 Roma (Italy); Miller, H. R.; Eggen, J.; Maune, J. [Department of Physics and Astronomy Georgia State University, GA 30303-3083 (United States); Popovic, L. C. [Astronomical Observatory, Volgina 7, 11160, Belgrade 74 (Serbia); Simic, S. [Isaac Newton Institute of Chile, Yugoslavia Branch, Belgrade (Serbia); Kuulkers, E. [European Space Astronomy Centre, SRE-O, Villanueva de la Canada, Madrid (Spain); Vercellone, S. [INAF/IASF Palermo Via Ugo La Malfa 153, 90146 Palermo (Italy); Pucella, G. [ENEA-Frascati, Via E. Fermi 45, I-00044 Frascati, Roma (Italy); Verrecchia, F.; Pittori, C.; Giommi, P. [ASI-ASDC, Via G. Galilei, I-00044 Frascati, Roma (Italy); Barbiellini, G. [Dipartimento di Fisica and INFN Trieste, Via Valerio 2, I-34127 Trieste (Italy); Bulgarelli, A. [INAF/IASF-Bologna, Via Gobetti 101, I-40129 Bologna (Italy); Cattaneo, P. W., E-mail: email@example.com [INFN-Pavia, Via Bassi 6, I-27100 Pavia (Italy)
Subaru weak lensing measurement of a z = 0.81 cluster discovered by the Atacama Cosmology Telescope Survey
NASA Astrophysics Data System (ADS)
We present a Subaru weak lensing measurement of ACT-CL J0022.2-0036, one of the most luminous, high-redshift (z = 0.81) Sunyaev-Zel'dovich (SZ) clusters discovered in the 268 deg2 equatorial region survey of the Atacama Cosmology Telescope that overlaps with Sloan Digital Sky Survey (SDSS) Stripe 82 field. Ours is the first weak lensing study with Subaru at such high redshifts. For the weak lensing analysis using i'-band images, we use a model-fitting (Gauss-Laguerre shapelet) method to measure shapes of galaxy images, where we fit galaxy images in different exposures simultaneously to obtain best-fitting ellipticities taking into account the different point spread functions (PSFs) in each exposure. We also take into account the astrometric distortion effect on galaxy images by performing the model fitting in the world coordinate system. To select background galaxies behind the cluster at z = 0.81, we use photometric redshift estimates for every galaxy derived from the co-added images of multi-passband Br'i'z'Y, with PSF matching/homogenization. After a photometric redshift cut for background galaxy selection, we detect the tangential weak lensing distortion signal with a total signal-to-noise ratio of about 3.7. By fitting a Navarro-Frenk-White model to the measured shear profile, we find the cluster mass to be M_{200bar{? }_m} = [7.5^{+3.2}_{-2.8}(stat.)^{+1.3}_{-0.6}(sys.)]� 10^{14} M_{odot } h^{-1}. The weak lensing-derived mass is consistent with previous mass estimates based on the SZ observation, with assumptions of hydrostatic equilibrium and virial theorem, as well as with scaling relations between SZ signal and mass derived from weak lensing, X-ray and velocity dispersion, within the measurement errors. We also show that the existence of ACT-CL J0022.2-0036 at z = 0.81 is consistent with the cluster abundance prediction of the ?-dominated cold dark matter structure formation model. We thus demonstrate the capability of Subaru-type ground-based images for studying weak lensing of high-redshift clusters.
Miyatake, Hironao; Nishizawa, Atsushi J.; Takada, Masahiro; Mandelbaum, Rachel; Mineo, Sogo; Aihara, Hiroaki; Spergel, David N.; Bickerton, Steven J.; Bond, J. Richard; Gralla, Megan; Hajian, Amir; Hilton, Matt; Hincks, Adam D.; Hughes, John P.; Infante, Leopoldo; Lin, Yen-Ting; Lupton, Robert H.; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Miyazaki, Satoshi; Moodley, Kavilan; Niemack, Michael D.; Oguri, Masamune; Price, Paul A.; Reese, Erik D.; Sif�n, Crist�bal; Wollack, Edward J.; Yasuda, Naoki
Gravitational lensing by globular clusters and dwarf galaxies-- the explanation of quasar-galaxy associations
NASA Astrophysics Data System (ADS)
Quasar-galaxy associations can be explained as gravitational lensing by globular clusters, located in the halos of the foreground galaxies and dwarf galaxies in small groups of galaxies. We propose an observational test for checking this hypothesis. We used the SUPERCOSMOS sky survey to find the overdensities of star-like sources with zero proper motions in the vicinities of the~foreground galaxies from the CfA3 catalog. The results obtained for 19413 galaxies are presented. We show the results of calculations of number densities of star-like sources with zero proper motions in the vicinity of 19413 galaxies. Two different effects can explain the observational data: lensing by globular clusters and lensing by dwarf galaxies. We carried out the CCD 3-color photometry with the 2.0-m telescope of the~Terskol Observatory and the 1.8-m telescope of the Bohyunsan Observatory (South Korea) to select extremely lensed objects around several galaxies for future spectroscopic observations. From ads Wed Jan 12 06:25:17 2005 Return-Path:
Yushchenko, A.; Kim, C.; Sergeev, A.
CFHTLenS tomographic weak lensing cosmological parameter constraints: Mitigating the impact of intrinsic galaxy alignments
NASA Astrophysics Data System (ADS)
We present a finely binned tomographic weak lensing analysis of the Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS) mitigating contamination to the signal from the presence of intrinsic galaxy alignments via the simultaneous fit of a cosmological model and an intrinsic alignment model. CFHTLenS spans 154 square degrees in five optical bands, with accurate shear and photometric redshifts for a galaxy sample with a median redshift of zm = 0.70. We estimate the 21 sets of cosmic shear correlation functions associated with six redshift bins, each spanning the angular range of 1.5 < ? < 35 arcmin. We combine this CFHTLenS data with auxiliary cosmological probes: the cosmic microwave background with data from WMAP7, baryon acoustic oscillations with data from Baryon Oscillation Spectroscopic Survey and a prior on the Hubble constant from the Hubble Space Telescope distance ladder. This leads to constraints on the normalization of the matter power spectrum ?8 = 0.799 � 0.015 and the matter density parameter ?m = 0.271 � 0.010 for a flat ? cold dark matter (?CDM) cosmology. For a flat wCDM cosmology, we constrain the dark energy equation-of-state parameter w = -1.02 � 0.09. We also provide constraints for curved ?CDM and wCDM cosmologies. We find the intrinsic alignment contamination to be galaxy-type dependent with a significant intrinsic alignment signal found for early-type galaxies, in contrast to the late-type galaxy sample for which the intrinsic alignment signal is found to be consistent with zero.
Heymans, Catherine; Grocutt, Emma; Heavens, Alan; Kilbinger, Martin; Kitching, Thomas D.; Simpson, Fergus; Benjamin, Jonathan; Erben, Thomas; Hildebrandt, Hendrik; Hoekstra, Henk; Mellier, Yannick; Miller, Lance; Van Waerbeke, Ludovic; Brown, Michael L.; Coupon, Jean; Fu, Liping; Harnois-D�raps, Joachim; Hudson, Michael J.; Kuijken, Konrad; Rowe, Barnaby; Schrabback, Tim; Semboloni, Elisabetta; Vafaei, Sanaz; Velander, Malin
We use a mock catalog of galaxies based on the COSMOS galaxy catalog, including information on photometric redshift (photo-z) and spectral energy distribution types of galaxies, in order to study how to define a galaxy subsample suitable for weak lensing tomography feasible with optical (and near-IR) multi-band data. Since most useful cosmological information arises from the sample variance limited regime for upcoming lensing surveys, a suitable subsample can be obtained by discarding a large fraction of galaxies that have less reliable photo-z estimations. We develop a method to efficiently identify photo-z outliers by monitoring the width of the posterior likelihood function of redshift estimation for each galaxy. This clipping method may allow us to obtain clean tomographic redshift bins (here three bins are considered) that have almost no overlap, by discarding more than {approx}70% of galaxies with ill-defined photo-zs corresponding to the number densities of remaining galaxies less than {approx}20 arcmin{sup -2} for a Subaru-type deep survey. Restricting the ranges of magnitudes and redshifts and/or adding near-IR data help us obtain a cleaner redshift binning. Using the Fisher information matrix formalism, we propagate photo-z errors into biases in the dark energy equation of state parameter w. We find that, by discarding most of the ill-defined photo-z galaxies, the bias in w can be reduced to a level comparable to the marginalized statistical error; however, the residual small systematic bias remains due to asymmetric scatters around the relation between photometric and true redshifts. We also use the mock catalog to estimate the cumulative signal-to-noise ratios (S/Ns) for measuring the angular cross-correlations of galaxies between finer photo-z bins, finding higher S/N values for the bins that include photo-z outliers.
Nishizawa, Atsushi J. [Astronomical Institute, Tohoku University, Aramaki Aobaku, Sendai 980-8578 (Japan); Takada, Masahiro [Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, 5-1-5 Kashiwa-no-Ha, Kashiwa City, Chiba 277-8582 (Japan); Hamana, Takashi; Furusawa, Hisanori, E-mail: firstname.lastname@example.com [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka City, Tokyo 181-8588 (Japan)
Random walks in cosmology: Weak lensing, the halo model, and reionization
NASA Astrophysics Data System (ADS)
This thesis discusses theoretical problems in three areas of cosmology: weak lensing, the halo model, and reionization. In weak lensing, we investigate the impact of the intrinsic alignment on the density-ellipticity correlations using the tidal torquing theory. Under the assumption of the Gaussianity of the tidal field, we find that the intrinsic alignment does not contaminate the density-ellipticity correlation even if the source clustering correlations are taken into account. The non-Gaussian contributions to both the intrinsic density-ellipticity and ellipticity- ellipticity correlations are often non-negligible. In a separate work, we discuss a useful scaling relation in weak lensing measurements. Given a foreground galaxy-density field or shear field, its cross-correlation with the shear field from a background population of source galaxies scales with the source redshift in a way that allows us to effectively measure geometrical distances as a function of redshift and thereby constrain dark energy properties without assuming anything about the galaxy-mass/mass power spectrum. Such a geometrical method can yield a ~ 0.03--0.07 [Special characters omitted.] measurement on the dark energy abundance and equation of state, for a photometric redshift accuracy of [Delta] z ~ 0.01--0.05 and a survey with median redshift of ~1. The geometrical method also provides a consistency check of the standard cosmological model because it is completely independent of structure formation. In the excursion set theory of the halo model, we derive the first-crossing distribution of random walks with a moving barrier of a general shape. Such a distribution is shown to satisfy an integral equation that can be solved by a simple matrix inversion, without the need for Monte Carlo simulations, making it useful for exploring a large parameter space. We discuss examples in which common analytic approximations fail, a failure that can be remedied using our method. In reionization, we calculate the large scale properties of the HII/HI and radiation distributions using the linear perturbation theory. Given the distribution and the spectrum of the ionizing sources, our formalism can be used to calculate the large scale bias of the HII regions from first principles by solving the equations of ionization balance and radiative transfer in Fourier space. We also discuss an approximate but easy way of solving these equations for UV dominated source spectra. Using the extended Press-Schechter model, we find: (1) reionization always proceeds inside-out, at least on large scales; (2) on sufficiently large scales, HII, HI and radiation exhibit a scale independent bias relative to dark matter; (3) the bias is suppressed on scales comparable to or smaller than the mean free path of the ionizing photons; (4) if the ionizing source spectrum is sufficiently soft, the HII bias closely tracks the source bias for most of the reionization process but drops precipitously after percolation; (5) if the ionizing source spectrum is hard, the HII bias drops in a more steady fashion throughout the reionization process. The tools developed here will be useful for interpreting future 21cm, CMB and Lyman-alpha forest observations, both to learn about the reionization astrophysics and to possibly extract interesting cosmological information.
Zhang, Jun
Gravitational lensing and dynamics in SL2S J02140-0535: probing the mass out to large radius
NASA Astrophysics Data System (ADS)
Context. Studying the density profiles of galaxy groups offers an important insight into the formation and evolution of the structures in the universe, since galaxy groups bridge the gap between single galaxies and massive clusters. Aims: We aim to probe the mass of SL2S J02140-0535, a galaxy group at z = 0.44 from the Strong Lensing Legacy Survey (SL2S), which has uncovered this new population of group-scale strong lenses. Methods: We combine strong lensing modeling and dynamical constraints. The strong lensing analysis is based on multi-band HST/ACS observations exhibiting strong lensing features that we have followed-up spectroscopically with VLT/FORS2. To constrain the scale radius of an NFW mass profile that cannot be constrained by strong lensing, we propose a new method by taking advantage of the large-scale dynamical information provided by VLT/FORS2 and KECK/LRIS spectroscopy of group members. Results: In constrast to other authors, we show that the observed lensing features in SL2S J02140-0535 belong to different background sources: one at z = 1.7 � 0.1 (photometric redshift) produces three images, while the other at z = 1.023 � 0.001 (spectroscopic redshift) has only a single image. Our unimodal NFW mass model reproduces these images very well. It is characterized by a concentration parameter c200 = 6.0 � 0.6, which is slightly greater than the value expected from ?CDM simulations for a mass of M200 ? 1 � 1014 M?. The spectroscopic analysis of group members also reveals a unimodal structure that exhibits no evidence of merging. The position angle of the halo is ? = 111.6 � 0.2, which agrees with the direction defined by the luminosity contours. We compare our dynamic mass estimate with an independent weak-lensing based mass estimate finding that both are consistent. Conclusions: Our combined lensing and dynamical analysis of SL2S J02140-0535 demonstrates the importance of spectroscopic information in reliably identifying the lensing features. Our findings argue that the system is a relaxed, massive galaxy group where mass is traced by light. This work shows a potentially useful method for constraining large-scale properties inaccessible to strong lensing, such as the scale radius of the NFW profile.
Verdugo, T.; Motta, V.; Mu�oz, R. P.; Limousin, M.; Cabanac, R.; Richard, J.
The Optical Gravitational Lensing Experiment. Gaia South Ecliptic Pole Field as Seen by OGLE-IV
NASA Astrophysics Data System (ADS)
We present a comprehensive analysis of the Gaia South Ecliptic Pole (GSEP) field, 5.3 square degrees area around the South Ecliptic Pole on the outskirts of the LMC, based on the data collected during the fourth phase of the Optical Gravitational Lensing Experiment, OGLE-IV. The GSEP field will be observed during the commissioning phase of the ESA Gaia space mission for testing and calibrating the Gaia instruments. We provide the photometric maps of the GSEP region containing the mean VI photometry of all detected stellar objects and their equatorial coordinates. We show the quality and completeness of the OGLE-IV photometry and color-magnitude diagrams of this region. We conducted an extensive search for variable stars in the GSEP field leading to the discovery of 6789 variable stars. In this sample we found 132 classical Cepheids, 686 RR Lyr type stars, 2819 long-period, and 1377 eclipsing variables. Several objects deserving special attention were also selected, including a new classical Cepheid in a binary eclipsing system. To provide empirical data for the Gaia Science Alert system we also conducted a search for optical transients. We discovered two firm type Ia supernovae and nine additional supernova candidates. To facilitate future Gaia supernovae detections we prepared a list of more than 1900 galaxies to redshift about 0.1 located in the GSEP field. Finally, we present the results of astrometric study of the GSEP field. With the 26 months time base of the presented here OGLE-IV data, proper motions of stars could be detected with the accuracy reaching 2 mas/yr. Astrometry allowed to distinguish galactic foreground variable stars detected in the GSEP field from LMC objects and to discover about 50 high proper motion stars (proper motion ? 100 mas/yr). Among them three new nearby white dwarfs were found. All data presented in this paper are available to the astronomical community from the OGLE Internet archive.
Soszy?ski, I.; Udalski, A.; Poleski, R.; Koz?owski, S.; Wyrzykowski, ?.; Pietrukowicz, P.; Szyma?ski, M. K.; Kubiak, M.; Pietrzy?ski, G.; Ulaczyk, K.; Skowron, J.
Cosmology with Minkowski functionals and moments of the weak lensing convergence field
NASA Astrophysics Data System (ADS)
We compare the efficiency of moments and Minkowski functionals (MFs) in constraining the subset of cosmological parameters (?m,w,?8) using simulated weak lensing convergence maps. We study an analytic perturbative expansion of the MFs [T. Matsubara, Phys. Rev. D 81, 083505 (2010); D. Munshi et al., Mon. Not. R. Astron. Soc. 419, 536 (2012)] in terms of the moments of the convergence field and of its spatial derivatives. We show that this perturbation series breaks down on smoothing scales below 5', while it shows a good degree of convergence on larger scales (�15'). Most of the cosmological distinguishing power is lost when the maps are smoothed on these larger scales. We also show that, on scales comparable to 1', where the perturbation series does not converge, cosmological constraints obtained from the MFs are approximately 1.5-2 times better than the ones obtained from the first few moments of the convergence distribution�provided that the latter include spatial information, either from moments of gradients or by combining multiple smoothing scales. Including a set of either these moments or the MFs can significantly tighten constraints on cosmological parameters, compared to the conventional method of using the power spectrum alone.
Petri, Andrea; Haiman, Zolt�n; Hui, Lam; May, Morgan; Kratochvil, Jan M.
Cross-correlation Weak Lensing of SDSS Galaxy Clusters I: Measurements
This is the first in a series of papers on the weak lensing effect caused by clusters of galaxies in Sloan Digital Sky Survey. The photometrically selected cluster sample, known as MaxBCG, includes {approx}130,000 objects between redshift 0.1 and 0.3, ranging in size from small groups to massive clusters. We split the clusters into bins of richness and luminosity and stack the surface density contrast to produce mean radial profiles. The mean profiles are detected over a range of scales, from the inner halo (25 kpc/h) well into the surrounding large scale structure (30 Mpc/h), with a significance of 15 to 20 in each bin. The signal over this large range of scales is best interpreted in terms of the cluster-mass cross-correlation function. We pay careful attention to sources of systematic error, correcting for them where possible and bounding them where not. We find that the profiles scale strongly with richness and luminosity. We find the signal within a given richness bin depends upon luminosity, suggesting that luminosity is more closely correlated with mass than galaxy counts. We split the samples by redshift but detect no significant evolution. The profiles are not well described by power laws. In a subsequent series of papers we invert the profiles to three-dimensional mass profiles, show that they are well fit by a halo model description, measure mass-to-light ratios and provide a cosmological interpretation.
Sheldon, Erin S.; Johnston, David E.; Scranton, Ryan; Koester, Ben P.; McKay, Timothy A.; Oyaizu, Hiroaki; Cunha, Carlos; Lima, Marcos; Lin, Huan; Frieman, Joshua A.; Wechsler, Risa H.; Annis, James; Mandelbaum, Rachel; Bahcall, Neta A.; Fukugita, Masataka
Lensing Effects on Gravitational Waves in a Clumpy Universe: Effects of Inhomogeneity on the Distance-Redshift Relation
NASA Astrophysics Data System (ADS)
The distance-redshift relation determined by means of gravitational waves in the clumpy universe is simulated numerically by taking into account the effects of gravitational lensing. It is assumed that all of the matter in the universe takes the form of randomly distributed point masses, each of which has the identical mass ML. Calculations are carried out in two extreme cases, ?>>GML/c2 and ?<
Yoo, Chul-Moon; Nakao, Ken-ichi; Kozaki, Hiroshi; Takahashi, Ryuichi
The dark matter environment of the Abell 901/902 supercluster: a weak lensing analysis of the HST STAGES survey
NASA Astrophysics Data System (ADS)
We present a high-resolution dark matter reconstruction of the z = 0.165 Abell 901/902 supercluster from a weak lensing analysis of the Hubble Space Telescope STAGES survey. We detect the four main structures of the supercluster at high significance, resolving substructure within and between the clusters. We find that the distribution of dark matter is well traced by the cluster galaxies, with the brightest cluster galaxies marking out the strongest peaks in the dark matter distribution. We also find a significant extension of the dark matter distribution of Abell 901a in the direction of an infalling X-ray group Abell 901?. We present mass, mass-to-light and mass-to-stellar mass ratio measurements of the structures and substructures that we detect. We find no evidence for variation of the mass-to-light and mass-to-stellar mass ratio between the different clusters. We compare our space-based lensing analysis with an earlier ground-based lensing analysis of the supercluster to demonstrate the importance of space-based imaging for future weak lensing dark matter `observations'.
Heymans, Catherine; Gray, Meghan E.; Peng, Chien Y.; van Waerbeke, Ludovic; Bell, Eric F.; Wolf, Christian; Bacon, David; Balogh, Michael; Barazza, Fabio D.; Barden, Marco; B�hm, Asmus; Caldwell, John A. R.; H�u�ler, Boris; Jahnke, Knud; Jogee, Shardha; van Kampen, Eelco; Lane, Kyle; McIntosh, Daniel H.; Meisenheimer, Klaus; Mellier, Yannick; S�nchez, Sebastian F.; Taylor, Andy N.; Wisotzki, Lutz; Zheng, Xianzhong
RINGFINDER: Automated Detection of Galaxy-scale Gravitational Lenses in Ground-based Multi-filter Imaging Data
NASA Astrophysics Data System (ADS)
We present RINGFINDER, a tool for finding galaxy-scale strong gravitational lenses in multi-band imaging data. By construction, the method is sensitive to configurations involving a massive foreground ETG and a faint, background, blue source. RINGFINDER detects the presence of blue residuals embedded in an otherwise smooth red light distribution by difference imaging in two bands. The method is automated for efficient application to current and future surveys, having originally been designed for the 150 deg2 Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We describe each of the steps of RINGFINDER. We then carry out extensive simulations to assess completeness and purity. For sources with magnification ? > 4, RINGFINDER reaches 42% (25%) completeness and 29% (86%) purity before (after) visual inspection. The completeness of RINGFINDER is substantially improved in the particular range of Einstein radii 0.''8 <= R Ein <= 2.''0 and lensed images brighter than g = 22.5, where it can be as high as ~70%. RINGFINDER does not introduce any significant bias in the source or deflector population. We conclude by presenting the final catalog of RINGFINDER CFHTLS galaxy-scale strong lens candidates. Additional information obtained with Hubble Space Telescope and Keck adaptive optics high-resolution imaging, and with Keck and Very Large Telescope spectroscopy, is used to assess the validity of our classification and measure the redshift of the foreground and the background objects. From an initial sample of 640,000 ETGs, RINGFINDER returns 2500 candidates, which we further reduce by visual inspection to 330 candidates. We confirm 33 new gravitational lenses from the main sample of candidates, plus an additional 16 systems taken from earlier versions of RINGFINDER. First applications are presented in the Strong Lensing Legacy Survey galaxy-scale lens sample paper series.
Gavazzi, Rapha�l; Marshall, Philip J.; Treu, Tommaso; Sonnenfeld, Alessandro
Very weak lensing in the CFHTLS wide: cosmology from cosmic shear in the linear regime
NASA Astrophysics Data System (ADS)
Aims:We present an exploration of weak lensing by large-scale structure in the linear regime, using the third-year (T0003) CFHTLS Wide data release. Our results place tight constraints on the scaling of the amplitude of the matter power spectrum ?8 with the matter density ?_m. Methods: Spanning 57 square degrees to i'AB = 24.5 over three independent fields, the unprecedented contiguous area of this survey permits high signal-to-noise measurements of two-point shear statistics from 1 arcmin to 4 degrees. Understanding systematic errors in our analysis is vital in interpreting the results. We therefore demonstrate the percent-level accuracy of our method using STEP simulations, an E/B-mode decomposition of the data, and the star-galaxy cross correlation function. We also present a thorough analysis of the galaxy redshift distribution using redshift data from the CFHTLS T0003 Deep fields that probe the same spatial regions as the Wide fields. Results: We find ?_8(?m / 0.25)0.64 = 0.785 � 0.043 using the aperture-mass statistic for the full range of angular scales for an assumed flat cosmology, in excellent agreement with WMAP3 constraints. The largest physical scale probed by our analysis is 85 Mpc, assuming a mean redshift of lenses of 0.5 and a ?CDM cosmology. This allows for the first time to constrain cosmology using only cosmic shear measurements in the linear regime. Using only angular scales ?> 85 arcmin, we find ?_8(?m / 0.25)lin0.53 = 0.837 � 0.084, which agree with the results from our full analysis. Combining our results with data from WMAP3, we find ?_m=0.248 � 0.019 and ?_8=0.771 � 0.029. Based on observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. This work is based in part on data products produced at Terapix and the Canadian Astronomy Data Centre as part of the Canada-France-Hawaii Telescope Legacy Survey, a collaborative project of NRC and CNRS. Appendix B is only available in electronic form at http://www.aanda.org
Fu, L.; Semboloni, E.; Hoekstra, H.; Kilbinger, M.; van Waerbeke, L.; Tereno, I.; Mellier, Y.; Heymans, C.; Coupon, J.; Benabed, K.; Benjamin, J.; Bertin, E.; Dor�, O.; Hudson, M. J.; Ilbert, O.; Maoli, R.; Marmo, C.; McCracken, H. J.; M�nard, B.
Analysis of spatially resolved IUE spectra of 0957+561A,B: A gravitationally lensed double quasar
NASA Technical Reports Server (NTRS)
A study of 18 IUE spectra of the gravitationally lensed quasar, 0957+561A,B was used to search for time delays between light variation in the 2 components. Evidence for substantial, rapid variability in Component A in 1980, followed by a light variation in the other component 20 months later is found. However, it is argued that these variations do not record the same event in the quasar, and so, cannot be used to derive a value for the Hubble constant. The cause of the rapid variation in Component A in 1980 is not understood, but it does not appear to be a microlensing event.
Altner, Bruce; Heap, Sara R.
Probing gravity at cosmological scales by measurements which test the relationship between gravitational lensing and matter overdensity.
The standard cosmology is based on general relativity (GR) and includes dark matter and dark energy and predicts a fixed relationship between the gravitational potentials responsible for gravitational lensing and the matter overdensity. Alternative theories of gravity often make different predictions. We propose a set of measurements which can test this relationship, thereby distinguishing between dark energy or matter models and models in which gravity differs from GR. Planned surveys will be able to measure E(G), an observational quantity whose expectation value is equal to the ratio of the Laplacian of the Newtonian potentials to the peculiar velocity divergence, to percent accuracy. This will easily separate alternatives such as the cold dark matter model with a cosmological constant, Dvali-Gabadadze-Porrati, TeVeS, and f(R) gravity. PMID:17930657
Zhang, Pengjie; Liguori, Michele; Bean, Rachel; Dodelson, Scott
The strongest gravitational lenses. III. The order statistics of the largest Einstein radii
NASA Astrophysics Data System (ADS)
Context. The Einstein radius of a gravitational lens is a key characteristic. It encodes information about decisive quantities such as halo mass, concentration, triaxiality, and orientation with respect to the observer. Therefore, the largest Einstein radii can potentially be utilised to test the predictions of the ?CDM model. Aims: Hitherto, studies have focussed on the single largest observed Einstein radius. We extend those studies by employing order statistics to formulate exclusion criteria based on the n largest Einstein radii and apply these criteria to the strong lensing analysis of 12 MACS clusters at z> 0.5. Methods: We obtain the order statistics of Einstein radii by a Monte Carlo approach, based on the semi-analytic modelling of the halo population on the past lightcone. After sampling the order statistics, we fit a general extreme value distribution to the first-order distribution, which allows us to derive analytic relations for the order statistics of the Einstein radii. Results: We find that the Einstein radii of the 12 MACS clusters are not in conflict with the ?CDM expectations. Our exclusion criteria indicate that, in order to exhibit tension with the concordance model, one would need to observe approximately twenty Einstein radii with ?eff ? 30?, ten with ?eff ? 35?, five with ?eff ? 42?, or one with ?eff ? 74? in the redshift range 0.5 ? z ? 1.0 on the full sky (assuming a source redshift of zs = 2). Furthermore, we find that, with increasing order, the haloes with the largest Einstein radii are on average less aligned along the line-of-sight and less triaxial. In general, the cumulative distribution functions steepen for higher orders, giving them better constraining power. Conclusions: A framework that allows the individual and joint order distributions of the n-largest Einstein radii to be derived is presented. From a statistical point of view, we do not see any evidence of an Einstein ring problem even for the largest Einstein radii of the studied MACS sample. This conclusion is consolidated by the large uncertainties that enter the lens modelling and to which the largest Einstein radii are particularly sensitive.
Waizmann, J.-C.; Redlich, M.; Meneghetti, M.; Bartelmann, M.
COSMOS: Stochastic Bias from Measurements of Weak Lensing and Galaxy Clustering
NASA Astrophysics Data System (ADS)
In the theory of structure formation, galaxies are biased tracers of the underlying matter density field. The statistical relation between galaxy and matter density field is commonly referred to as galaxy bias. In this paper, we test the linear bias model with weak-lensing and galaxy clustering measurements in the 2 deg2 COSMOS field. We estimate the bias of galaxies between redshifts z = 0.2 and z = 1 and over correlation scales between R = 0.2 h -1 Mpc and R = 15 h -1 Mpc. We focus on three galaxy samples, selected in flux (simultaneous cuts I 814W < 26.5 and Ks < 24) and in stellar mass (109 < M * < 1010 h -2 M ? and 1010 < M * < 1011 h -2 M ?). At scales R > 2 h -1 Mpc, our measurements support a model of bias increasing with redshift. The Tinker et al. fitting function provides a good fit to the data. We find the best-fit mass of the galaxy halos to be log (M 200/h -1 M ?) = 11.7+0.6 - 1.3 and log (M 200/h -1 M ?) = 12.4+0.2 - 2.9, respectively, for the low and high stellar-mass samples. In the halo model framework, bias is scale dependent with a change of slope at the transition scale between the one and the two halo terms. We detect a scale dependence of bias with a turndown at scale R = 2.3 � 1.5 h -1 Mpc, in agreement with previous galaxy clustering studies. We find no significant amount of stochasticity, suggesting that a linear bias model is sufficient to describe our data. We use N-body simulations to quantify both the amount of cosmic variance and systematic errors in the measurement.
Jullo, Eric; Rhodes, Jason; Kiessling, Alina; Taylor, James E.; Massey, Richard; Berge, Joel; Schimd, Carlo; Kneib, Jean-Paul; Scoville, Nick
Testing a phenomenologically extended DGP model with upcoming weak lensing surveys
NASA Astrophysics Data System (ADS)
A phenomenological extension of the well-known brane-world cosmology of Dvali, Gabadadze and Porrati (eDGP) has recently been proposed. In this model, a cosmological-constant-like term is explicitly present as a non-vanishing tension ? on the brane, and an extra parameter ? tunes the cross-over scale rc, the scale at which higher dimensional gravity effects become non negligible. Since the Hubble parameter in this cosmology reproduces the same ?CDM expansion history, we study how upcoming weak lensing surveys, such as Euclid and DES (Dark Energy Survey), can confirm or rule out this class of models. We perform Monte Carlo Markov Chain simulations to determine the parameters of the model, using Type Ia Supernov�, H(z) data, Gamma Ray Bursts and Baryon Acoustic Oscillations. We also fit the power spectrum of the temperature anisotropies of the Cosmic Microwave Background to obtain the correct normalisation for the density perturbation power spectrum. Then, we compute the matter and the cosmic shear power spectra, both in the linear and non-linear r�gimes. The latter is calculated with the two different approaches of Hu and Sawicki (2007) (HS) and Khoury and Wyman (2009) (KW). With the eDGP parameters coming from the Markov Chains, KW reproduces the ?CDM matter power spectrum at both linear and non-linear scales and the ?CDM and eDGP shear signals are degenerate. This result does not hold with the HS prescription. Indeed, Euclid can distinguish the eDGP model from ?CDM because their expected power spectra roughly differ by the 3? uncertainty in the angular scale range 700lesssimllesssim3000; on the contrary, the two models differ at most by the 1? uncertainty over the range 500lesssimllesssim3000 in the DES experiment and they are virtually indistinguishable.
Camera, Stefano; Diaferio, Antonaldo; Cardone, Vincenzo F.
Atmospheric PSF Interpolation for Weak Lensing in Short Exposure Imaging Data
A main science goal for the Large Synoptic Survey Telescope (LSST) is to measure the cosmic shear signal from weak lensing to extreme accuracy. One difficulty, however, is that with the short exposure time ({approx_equal}15 seconds) proposed, the spatial variation of the Point Spread Function (PSF) shapes may be dominated by the atmosphere, in addition to optics errors. While optics errors mainly cause the PSF to vary on angular scales similar or larger than a single CCD sensor, the atmosphere generates stochastic structures on a wide range of angular scales. It thus becomes a challenge to infer the multi-scale, complex atmospheric PSF patterns by interpolating the sparsely sampled stars in the field. In this paper we present a new method, psfent, for interpolating the PSF shape parameters, based on reconstructing underlying shape parameter maps with a multi-scale maximum entropy algorithm. We demonstrate, using images from the LSST Photon Simulator, the performance of our approach relative to a 5th-order polynomial fit (representing the current standard) and a simple boxcar smoothing technique. Quantitatively, psfent predicts more accurate PSF models in all scenarios and the residual PSF errors are spatially less correlated. This improvement in PSF interpolation leads to a factor of 3.5 lower systematic errors in the shear power spectrum on scales smaller than {approx} 13, compared to polynomial fitting. We estimate that with psfent and for stellar densities greater than {approx_equal}1/arcmin{sup 2}, the spurious shear correlation from PSF interpolation, after combining a complete 10-year dataset from LSST, is lower than the corresponding statistical uncertainties on the cosmic shear power spectrum, even under a conservative scenario.
Chang, C.; Marshall, P.J.; Jernigan, J.G.; Peterson, J.R.; Kahn, S.M.; Gull, S.F.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, S.; Meert, A.
This is the first in a series of papers on the weak lensing effect caused by clusters of galaxies in Sloan Digital Sky Survey. The photometrically selected cluster sample, known as MaxBCG, includes approx130,000 objects between redshift 0.1 and 0.3, ranging in size from small groups to massive clusters. We split the clusters into bins of richness and luminosity and stack the surface density contrast to produce mean radial profiles. The mean profiles are detected over a range of scales, from the inner halo (25 kpc h {sup -1}) well into the surrounding large-scale structure (30 Mpc h {sup -1}), with a significance of 15 to 20 in each bin. The signal over this large range of scales is best interpreted in terms of the cluster-mass cross-correlation function. We pay careful attention to sources of systematic error, correcting for them where possible. The resulting signals are calibrated to the approx10% level, with the dominant remaining uncertainty being the redshift distribution of the background sources. We find that the profiles scale strongly with richness and luminosity. We find that the signal within a given richness bin depends upon luminosity, suggesting that luminosity is more closely correlated with mass than galaxy counts. We split the samples by redshift but detect no significant evolution. The profiles are not well described by power laws. In a subsequent series of papers, we invert the profiles to three-dimensional mass profiles, show that they are well fit by a halo model description, measure mass-to-light ratios, and provide a cosmological interpretation.
Sheldon, Erin S. [Brookhaven National Laboratory, Upton, New York, NY 11973 (United States); Johnston, David E. [Department of Astronomy, 105-24, California Institute of Technology, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Scranton, Ryan [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260 (United States); Koester, Benjamin P.; Oyaizu, Hiroaki; Cunha, Carlos; Lima, Marcos; Frieman, Joshua A. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue Chicago, IL 60637 (United States); McKay, Timothy A. [Department of Physics, University of Michigan, 500 East University, Ann Arbor, MI 48109-1120 (United States); Lin Huan; Annis, James [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States); Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department and Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94305 (United States); Mandelbaum, Rachel [Department of Physics, Jadwin Hall, Princeton University, Princeton, NJ 08544 (United States); Bahcall, Neta A. [Princeton University Observatory, Peyton Hall, Princeton, NJ 08544 (United States); Fukugita, Masataka [Institute for Cosmic Ray Research, University of Tokyo, 5-1-5 Kashiwa, Kashiwa City, Chiba 277-8582 (Japan)
Joint analysis of cluster number counts and weak lensing power spectrum to correct for the super-sample covariance
NASA Astrophysics Data System (ADS)
A coherent over- or under-density contrast across a finite survey volume causes an upward- or downward fluctuation in the observed number of haloes. This fluctuation in halo number adds a significant co-variant scatter in the observed amplitudes of weak lensing power spectrum at non-linear, small scales - the so-called super-sample variance or the halo sample variance. In this paper, we show that by measuring both the number counts of clusters and the power spectrum in the same survey region, we can mitigate this loss of information and significantly enhance the scientific return from the upcoming surveys. First, using the halo model approach, we derive the cross-correlation between the halo number counts and the weak lensing power spectrum, taking into account the super-sample covariance effect, which well matches the distributions measured from 1000 realizations for a ?-dominated cold dark matter model. Then we show that adding the observed number counts of massive haloes with M ? 1014 M?/h can significantly improve the information content of weak lensing power spectrum, almost recovering the Gaussian information up to lmax ? 1000, if the average mass profiles of the massive haloes are known, which can be estimated from stacked lensing. When combined with the halo number counts for M > 3 or 1 � 1014 M? h-1, the improvement is up to a factor of 1.4 or 2 at lmax ? 1000-2000, equivalent to a factor of 2 or 4 times larger survey volume, compared to the power spectrum measurement alone.
Takada, Masahiro; Spergel, David N.
Development of Gravidynamical Equations for a Weakly Gravitating Body in the Vicinity of Absolute Zero Temperature
NASA Astrophysics Data System (ADS)
the framework of this model bodies have fuzzy outlines and are represented by means of spheroidal forms. The consistency of the statistical model with the Einstein general relativity3,4,5 has been shown. In the work6, which is a continuation of the paper2, it was investigated a slowly evolving in time process of a gravitational compression (contraction) of a spheroidal body close to an unstable me�hanical equilibrium state (a low mass flow), therefore the process of the gravitational contraction appears slowly developing in time (the case of unobservable velocities of particles composing a spheroidal body). For this case in the work7 it has been shown that the strength and potential of the gravitational field of a slowly contracting spheroidal body satisfy a differential equation of the second order of the parabolic type for the case of unobservable velocities of particles. Therefore gravitational waves of a soliton type are propagated in a weakly gravitating spheroidal body if values of velocities are unobservable. body. In the connection with the above-given statements, in the present paper the following assumptions are used: 1.The spheroidal body under consideration is homogeneous in its chemical structure, i.e. it consists of identical particles with the mass m0. 2.The spheroidal body is not subjected to influence of external fields and bodies. 3.The spheroidal body is isothermal and has temperature close to the absolute zero. 4.The concentration gradient is not too large in the sense that interphase boundaries are absent inside the spheroidal body. 5. In view of low values of the temperature the heat conduction and viscosity processes are not important, which allows to describe the rotation of the spheroidal body as a whole, while movement of flows of particles inside the weakly gravitating spheroidal body is modeled by means of a motion of an ideal medium (the case of observable velocities of particles). 6.Since the process of the gravitational compression (contraction) of the spheroidal body is weak and viscosity is absent, we regard the motion of the continuous medium to be non-turbulent. modeled by means of an ideal liquid. It is determined the connection of this equation with an equation of motion of a particle in a noninertial frame of reference. A gravimagnetic field is introduced in this paper. It is obtained the scalar and vector potentials as well as the Lagrange function of a particle moving in a gravitational and gravimagnetic fields. It is derived the equations of hyperbolic type for the gravitational field of a weakly gravitating spheroidal body under observable values of velocities of particles composing it. 1. A.M.Krot, Achievements in Modern Radioelectronics, special issue "Cosmic Radiophysics", no.8, pp.66- 2. A.M.Krot, Proc. SPIE 13th Symp."AeroSense", Orlando, Florida, April 5-9,1999, vol.3710,pp.1248-1259. 3. L.D.Landau and E.M.Lifshitz, Classical Theory of Fields, Addison-Wesley, 1951. 4. S.Weinberg, Gravitation and Cosmology, John Wiley and Sons, New York, 1972. 5. C.W.Misner, K.S.Thorne, and J.A.Wheeler, Gravitation, W.H.Freeman and Co., San Francisco, 1973. 6. A.M.Krot, Proc. SPIE 14th Symp."AeroSense",Orlando,Florida,April 24-28,2000,vol.4038,pp.1318-1329. 7. A.M.Krot, Proc. SPIE 15th Symp."AeroSense",Orlando,Florida,April 16-20,2001,vol.4394,pp.1271-1282.
Krot, Alexander M.
Ly? absorbers in motion: consequences of gravitational lensing for the cosmological redshift drift experiment
NASA Astrophysics Data System (ADS)
The evolution of the expansion rate of the Universe results in a drift in the redshift of distant sources over time. A measurement of this drift would provide us with a direct probe of expansion history. The Lyman ? (Ly?) forest has been recognized as the best candidate for this experiment, but the signal would be weak and it will take next generation large telescopes coupled with ultrastable high-resolution spectrographs to reach the cm s-1 resolution required. One source of noise that has not yet been assessed is the transverse motion of Ly? absorbers, which varies the gravitational potential in the line of sight and subsequently shifts the positions of background absorption lines. We examine the relationship between the pure cosmic signal and the observed redshift drift in the presence of moving Ly? clouds, particularly the collapsed structures associated with Lyman limit systems and damped Ly? systems. Surprisingly, the peculiar velocities and peculiar accelerations both enter the expression, although the acceleration term stands alone as an absolute error, whilst the velocity term appears as a fractional noise component. An estimate of the magnitude of the noise reassures us that the motion of the Ly? absorbers will not pose a threat to the detection of the signal. Research undertaken as part of the Commonwealth Cosmology Initiative (www.thecci.org), an international collaboration supported by the Australian Research Council (ARC). E-mail: firstname.lastname@example.com (MK); email@example.com (GFL)
Killedar, Madhura; Lewis, Geraint F.
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses. XI. Techniques for time delay measurement in presence of microlensing
NASA Astrophysics Data System (ADS)
Measuring time delays between the multiple images of gravitationally lensed quasars is now recognized as a competitive way to constrain the cosmological parameters, and it is complementary with other cosmological probes. This requires long and well sampled optical light curves of numerous lensed quasars, such as those obtained by the COSMOGRAIL collaboration. High-quality data from our monitoring campaign call for novel numerical techniques to robustly measure the delays, as well as the associated random and systematic uncertainties, even in the presence of microlensing variations. We propose three different point estimators to measure time delays, which are explicitly designed to handle light curves with extrinsic variability. These methods share a common formalism, which enables them to process data from n-image lenses. Since the estimators rely on significantly contrasting ideas, we expect them to be sensitive to different bias sources. For each method and data set, we empirically estimate both the precision and accuracy (bias) of the time delay measurement using simulated light curves with known time delays that closely mimic the observations. Finally, we test the self-consistency of our approach, and we demonstrate that our bias estimation is serviceable. These new methods, including the empirical uncertainty estimator, will represent the standard benchmark for analyzing the COSMOGRAIL light curves.
Tewes, M.; Courbin, F.; Meylan, G.
A Weak Lensing Study of X-ray Groups in the Cosmos Survey: Form and Evolution of the Mass-Luminosity Relation
NASA Astrophysics Data System (ADS)
Measurements of X-ray scaling laws are critical for improving cosmological constraints derived with the halo mass function and for understanding the physical processes that govern the heating and cooling of the intracluster medium. In this paper, we use a sample of 206 X-ray-selected galaxy groups to investigate the scaling relation between X-ray luminosity (L X) and halo mass (M 200) where M 200 is derived via stacked weak gravitational lensing. This work draws upon a broad array of multi-wavelength COSMOS observations including 1.64 degrees2 of contiguous imaging with the Advanced Camera for Surveys to a limiting magnitude of I F814W = 26.5 and deep XMM-Newton/Chandra imaging to a limiting flux of 1.0 � 10-15 erg cm-2 s-1 in the 0.5-2 keV band. The combined depth of these two data sets allows us to probe the lensing signals of X-ray-detected structures at both higher redshifts and lower masses than previously explored. Weak lensing profiles and halo masses are derived for nine sub-samples, narrowly binned in luminosity and redshift. The COSMOS data alone are well fit by a power law, M 200 vprop (L X)?, with a slope of ? = 0.66 � 0.14. These results significantly extend the dynamic range for which the halo masses of X-ray-selected structures have been measured with weak gravitational lensing. As a result, tight constraints are obtained for the slope of the M-L X relation. The combination of our group data with previously published cluster data demonstrates that the M-L X relation is well described by a single power law, ? = 0.64 � 0.03, over two decades in mass, M 200 ~ 1013.5-1015.5 h -1 72 M sun. These results are inconsistent at the 3.7? level with the self-similar prediction of ? = 0.75. We examine the redshift dependence of the M-L X relation and find little evidence for evolution beyond the rate predicted by self-similarity from z ~ 0.25 to z ~ 0.8. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc, under NASA contract NAS 5-26555; also based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory under Large Program 175.A-0839, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under cooperative agreement with the National Science Foundation; the National Radio Astronomy Observatory which is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc ; and the Canada-France-Hawaii Telescope with MegaPrime/MegaCam operated as a joint project by the Canada-France-Hawaii-Telescope Corporation, CEA/DAPNIA, the National Research Council of Canada, the Canadian Astronomy Data Centre, the Centre National de la Recherche Scientifique de France, TERAPIX and the University of Hawaii.
Leauthaud, Alexie; Finoguenov, Alexis; Kneib, Jean-Paul; Taylor, James E.; Massey, Richard; Rhodes, Jason; Ilbert, Olivier; Bundy, Kevin; Tinker, Jeremy; George, Matthew R.; Capak, Peter; Koekemoer, Anton M.; Johnston, David E.; Zhang, Yu-Ying; Cappelluti, Nico; Ellis, Richard S.; Elvis, Martin; Giodini, Stefania; Heymans, Catherine; Le F�vre, Oliver; Lilly, Simon; McCracken, Henry J.; Mellier, Yannick; R�fr�gier, Alexandre; Salvato, Mara; Scoville, Nick; Smoot, George; Tanaka, Masayuki; Van Waerbeke, Ludovic; Wolk, Melody
The Spatial Structure of the Cosmic X-Ray Background: Correlation with Local Galaxies and Gravitational Lensing by Clusters.
NASA Astrophysics Data System (ADS)
We investigate two contributions to the spatial structure of the Cosmic X-ray Background (CXB). We first study the contribution of the local universe to the CXB by correlating 67 Einstein X-ray fields (.1--3.5 keV) with the APM galaxy catalog (E<19). We compute the two point correlation function W_xg both at zero lag and at nonzero-lag. We detect a >3 sigma correlation signal. We test the validity of our results by using various control data sets. Slicing the galaxy catalog into various magnitude intervals allows us to examine the contribution of different redshift shells. The energy dependence is studied by computing W_xg in the softer and harder band. By fitting the amplitude and the angular dependence of W_xg, we investigate the contribution to the CXB of the catalogued galaxies themselves and of X-ray sources spatially associated with them. Gravitational lensing by intervening matter could also affect the spatial structure of the CXB. We focus on the lensing effect of clusters of galaxies on the apparent distribution of point sources which make up most (if not all) of the CXB. We model the clusters as Singular Isothermal Spheres and consider three reasonable extensions of the log N-log S relation observed by ROSAT. By setting a flux threshold for the resolution of point sources, we consider both the number counts of resolved sources and the intensity of the unresolved component of the CXB. We find that both of these quantities are significantly affected by the lensing effect within a narrow ring located at the critical radius of the cluster. We show that the effect could be detectable by AXAF. Aside from constraining models of the CXB, this lensing effect could be used to probe the potential of clusters of galaxies. This work was supported by NASA under grant NAGW 2507.
Refregier, A.; Helfand, D. J.; Loeb, A.; McMahon, R. G.
The shapes of distant galaxies are sheared by intervening galaxy clusters. We examine this effect in Stripe 82, a 275 deg{sup 2} region observed multiple times in the Sloan Digital Sky Survey (SDSS) and co-added to achieve greater depth. We obtain a mass-richness calibration that is similar to other SDSS analyses, demonstrating that the co-addition process did not adversely affect the lensing signal. We also propose a new parameterization of the effect of tomography on the cluster lensing signal which does not require binning in redshift, and we show that using this parameterization we can detect tomography for stacked clusters at varying redshifts. Finally, due to the sensitivity of the tomographic detection to accurately marginalize over the effect of the cluster mass, we show that tomography at low redshift (where dependence on exact cosmological models is weak) can be used to constrain mass profiles in clusters.
Simet, Melanie; Dodelson, Scott [Department of Astronomy and Astrophysics, University of Chicago, Chicago, IL 60637 (United States); Kubo, Jeffrey M.; Annis, James T.; Hao Jiangang; Johnston, David; Lin, Huan; Soares-Santos, Marcelle [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Reis, Ribamar R. R. [Instituto de Fisica, Universidade Federal do Rio de Janeiro (Brazil); Seo, Hee-Jong [Berkeley Center for Cosmological Physics and Berkeley Lab, University of California, Berkeley, CA 94720 (United States)
Slaying Systematics: Maximizing Cosmological Power from HST-Measured Weak Lensing Masses of High-Redshift Clusters
NASA Astrophysics Data System (ADS)
We aim to calibrate the SZ mass-scaling relation at z > 0.7 with high-quality weak-lensing measurements. We have already been awarded 60 orbits of HST imaging, and we seek to acquire complimentary i-band photometry for 15 clusters in order to nearly eliminate the dominant systematic in the lensing measurement: contamination by cluster galaxies. By combining HST imaging with deep I-band imaging, we can eliminate 95% of contaminating galaxies, thus enabling us to measure the mass-scaling normalization to 8% accuracy at 0.7 < z < 1.2. With such a calibration, the SPT clusters sample should improve constraints on sigma_8 and w by factors of 3 and 2, respectively, over CMB-only constraints, plus greatly improve redshift evolution studies when combined with low-redshift cluster samples.
Benson, Bradford; Applegate, Douglas; Schrabback, Tim; Carlstrom, John; Dietrich, Joerg; von der Linden, Anja; Allen, Steve
COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses. XIV. Time delay of the doubly lensed quasar SDSS J1001+5027
NASA Astrophysics Data System (ADS)
This paper presents optical R-band light curves and the time delay of the doubly imaged gravitationally lensed quasar SDSS J1001+5027 at a redshift of 1.838. We have observed this target for more than six years, between March 2005 and July 2011, using the 1.2-m Mercator Telescope, the 1.5-m telescope of the Maidanak Observatory, and the 2-m Himalayan Chandra Telescope. Our resulting light curves are composed of 443 independent epochs, and show strong intrinsic quasar variability, with an amplitude of the order of 0.2 magnitudes. From this data, we measure the time delay using five different methods, all relying on distinct approaches. One of these techniques is a new development presented in this paper. All our time-delay measurements are perfectly compatible. By combining them, we conclude that image A is leading B by 119.3 � 3.3 days (1?, 2.8% uncertainty), including systematic errors. It has been shown recently that such accurate time-delay measurements offer a highly complementary probe of dark energy and spatial curvature, as they independently constrain the Hubble constant. The next mandatory step towards using SDSS J1001+5027 in this context will be the measurement of the velocity dispersion of the lensing galaxy, in combination with deep Hubble Space Telescope imaging. Based on observations made with the 2.0-m Himalayan Chandra Telescope (Hanle, India), the 1.5-m AZT-22 telescope (Maidanak Observatory, Uzbekistan), and the 1.2-m Mercator Telescope. Mercator is operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrof�sica de Canarias.Light curves are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A44
Rathna Kumar, S.; Tewes, M.; Stalin, C. S.; Courbin, F.; Asfandiyarov, I.; Meylan, G.; Eulaers, E.; Prabhu, T. P.; Magain, P.; Van Winckel, H.; Ehgamberdiev, Sh.
Cross-correlation Weak Lensing of SDSS Galaxy Clusters III: Mass-to-light Ratios
We present measurements of the excess mass-to-light ratio measured around MaxBCG galaxy clusters observed in the SDSS. This red sequence cluster sample includes objects from small groups with M{sub 200} {approx} 5 x 10{sup 12}h{sup -1}M{sub {circle_dot}} to clusters with M{sub 200} {approx} 5 x 10{sup 15}h{sup -1}M{sub {circle_dot}}. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean {Delta}{yields}(r) = {rho}(r) -- {bar {rho}} for clusters in bins of richness and optical luminosity. We also measure the excess {sup 0.25}i-band luminosity density {Delta}{ell}(r) = {ell}(r) -- {bar {ell}}. For both mass and light, we de-project the profiles to produce 3D mass and light profiles over scales from 25h{sup -1} kpc to 22h{sup -1} Mpc. From these profiles we calculate the cumulative excess mass {Delta}M(r) and excess light {Delta}L(r) as a function of separation from the BCG. On small scales, where {rho}(r) >> {bar {rho}}, the integrated mass-to-light profile ({Delta}M/{Delta}L)(r) may be interpreted as the cluster mass-to-light ratio. We find the ({Delta}M/{Delta}L){sub 200}, the mass-to-light ratio within r{sub 200}, scales with cluster mass as a power law with index 0.33{+-}0.02. On large scales, where {rho}(r) {approx} {bar {rho}}, the {Delta}M/{Delta}L approaches an asymptotic value independent of scale or cluster richness. For small groups, the mean ({Delta}M/{Delta}L){sub 200} is much smaller than the asymptotic value, while for large clusters ({Delta}M/{Delta}L)200 is consistent with the asymptotic value. This asymptotic value should be proportional to the mean mass-to-light ratio of the universe {l_angle}M/L{r_angle}. We find {l_angle}M/L{r_angle} b{sup -2}{sub M/L} = 362 {+-} 54h measured in the {sup 0.25}i-bandpass. The parameter b{sup 2}{sub M/L} is primarily a function of the bias of the L {approx}< L* galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find {Omega}{sub m}b{sup -2}{sub M/L}= 0.20 {+-} 0.03, independent of the Hubble parameter.
Sheldon, Erin S.; Johnston, David E.; Masjedi, Morad; McKay, Timothy A.; Blanton, Michael R.; Scranton, Ryan; Wechsler, Risa H.; Koester, Ben P.; Hansen, Sarah M.; Frieman, Joshua A.; Annis, James
We present measurements of the excess mass-to-light ratio (M/L) measured around MaxBCG galaxy clusters observed in the Sloan Digital Sky Survey. This red-sequence cluster sample includes objects from small groups with M {sub 200} approx 5 x 10{sup 12} h {sup -1} M {sub sun} to clusters with M {sub 200} approx 10{sup 15} h {sup -1} M {sub sun}. Using cross-correlation weak lensing, we measure the excess mass density profile above the universal mean DELTArho(r)=rho(r)-rho-bar for clusters in bins of richness and optical luminosity. We also measure the excess luminosity density DELTAl(r)=l(r)-l-bar measured in the z = 0.25 i band. For both mass and light, we de-project the profiles to produce three-dimensional mass and light profiles over scales from 25 h {sup -1} kpc to 22 h {sup -1} Mpc. From these profiles we calculate the cumulative excess mass DELTAM(r) and excess light DELTAL(r) as a function of separation from the BCG. On small scales, where rho(r)>>rho-bar, the integrated mass-to-light profile (DELTAM/DELTAL)(r) may be interpreted as the cluster M/L. We find the (DELTAM/DELTAL){sub 200}, the M/L within r {sub 200}, scales with cluster mass as a power law with index 0.33 +- 0.02. On large scales, where rho(r)approxrho-bar, the DELTAM/DELTAL approaches an asymptotic value independent of cluster richness. For small groups, the mean (DELTAM/DELTAL){sub 200} is much smaller than the asymptotic value, while for large clusters (DELTAM/DELTAL){sub 200} is consistent with the asymptotic value. This asymptotic value should be proportional to the mean M/L of the universe (M/L). We find (M/L)b{sup -2} {sub M/L} = 362 +- 54h (statistical). There is additional uncertainty in the overall calibration at the approx10% level. The parameter b {sup 2} {sub M/L} is primarily a function of the bias of the L approx< L {sub *} galaxies used as light tracers, and should be of order unity. Multiplying by the luminosity density in the same bandpass we find OMEGA {sub m}b{sup -2} {sub M/L} = 0.20 +- 0.03, independent of the Hubble parameter.
Sheldon, Erin S. [Brookhaven National Laboratory, Upton, NY 11973 (United States); Johnston, David E. [Department of Astronomy, 105-24, California Institute of Technology, 1201 East California Boulevard, Pasadena, CA 91125 (United States); Masjedi, Morad; Blanton, Michael R. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); McKay, Timothy A. [Department of Physics, University of Michigan, 500 East University, Ann Arbor, MI 48109-1120 (United States); Scranton, Ryan [Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara Street, Pittsburgh, PA 15260 (United States); Wechsler, Risa H. [Kavli Institute for Particle Astrophysics and Cosmology, Physics Department, and Stanford Linear Accelerator Center, Stanford University, Stanford, CA 94305 (United States); Koester, Benjamin P.; Hansen, Sarah M.; Frieman, Joshua A. [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue Chicago, IL 60637 (United States); Annis, James [Fermi National Accelerator Laboratory, P.O. Box 500, Batavia, IL 60510 (United States)
Probing the neutrino mass hierarchy with cosmic microwave background weak lensing
NASA Astrophysics Data System (ADS)
We forecast constraints on cosmological parameters with primary cosmic microwave background (CMB) anisotropy information and weak lensing reconstruction with a future post-Planck CMB experiment, the Cosmic Origins Explorer (COrE), using oscillation data on the neutrino mass splittings as prior information. Our Markov chain Monte Carlo (MCMC) simulations in flat models with a non-evolving equation of state of dark energy w give typical 68 per cent upper bounds on the total neutrino mass of 0.136 and 0.098 eV for the inverted and normal hierarchies, respectively, assuming the total summed mass is close to the minimum allowed by the oscillation data for the respective hierarchies (0.10 and 0.06 eV). Including geometric information from future baryon acoustic oscillation measurements with the complete Baryon Oscillation Spectroscopic Survey, Type Ia supernovae distance moduli from Wide-Field Infrared Survey Telescope (WFIRST) and a realistic prior on the Hubble constant, these upper limits shrink to 0.118 and 0.080 eV for the inverted and normal hierarchies, respectively. Addition of these distance priors also yields per cent-level constraints on w. We find tension between our MCMC results and the results of a Fisher matrix analysis, most likely due to a strong geometric degeneracy between the total neutrino mass, the Hubble constant and w in the unlensed CMB power spectra. If the minimal-mass, normal hierarchy were realized in nature, the inverted hierarchy should be disfavoured by the full data combination at typically greater than the 2? level. For the minimal-mass inverted hierarchy, we compute the Bayes factor between the two hierarchies for various combinations of our forecast data sets, and find that the future cosmological probes considered here should be able to provide 'strong' evidence (odds ratio 12:1) for the inverted hierarchy. Finally, we consider potential biases of the other cosmological parameters from assuming the wrong hierarchy and find that all biases on the parameters are below their 1? marginalized errors.
Hall, Alex C.; Challinor, Anthony
Gravitational Lens Models Based on Submillimeter Array Imaging of Herschel-selected Strongly Lensed Sub-millimeter Galaxies at z > 1.5
NASA Astrophysics Data System (ADS)
Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S 500 > 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r half) and far-infrared luminosities (L FIR) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z lens > 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 ?m flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L FIR (median L FIR = 7.9 � 1012 L ?) and two decades in FIR luminosity surface density (median ?FIR = 6.0 � 1011 L ? kpc-2). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift. IMAGING OF HERSCHEL
Bussmann, R. S.; P�rez-Fournon, I.; Amber, S.; Calanog, J.; Gurwell, M. A.; Dannerbauer, H.; De Bernardis, F.; Fu, Hai; Harris, A. I.; Krips, M.; Lapi, A.; Maiolino, R.; Omont, A.; Riechers, D.; Wardlow, J.; Baker, A. J.; Birkinshaw, M.; Bock, J.; Bourne, N.; Clements, D. L.; Cooray, A.; De Zotti, G.; Dunne, L.; Dye, S.; Eales, S.; Farrah, D.; Gavazzi, R.; Gonz�lez Nuevo, J.; Hopwood, R.; Ibar, E.; Ivison, R. J.; Laporte, N.; Maddox, S.; Mart�nez-Navajas, P.; Michalowski, M.; Negrello, M.; Oliver, S. J.; Roseboom, I. G.; Scott, Douglas; Serjeant, S.; Smith, A. J.; Smith, Matthew; Streblyanska, A.; Valiante, E.; van der Werf, P.; Verma, A.; Vieira, J. D.; Wang, L.; Wilner, D.
Constrains on f( T) gravity with the strong gravitational lensing data
NASA Astrophysics Data System (ADS)
Strong lensing is an effective way to probing the properties of dark energy. In this paper, we use the strong lensing data to constrain the f( T) theory, which is a new modified gravity to explain the present accelerating cosmic expansion without the need of dark energy. In our discussion, the CMB and BAO data are also added to constrain model parameters tightly and three different f( T) models are studied. We find that strong lensing has an important role on constraining f( T) models, and once the CMB+BAO data is added, a tighter constraint is obtained. However, the consistency of our result with what is obtained from SNIa+CMB+BAO is actually model-dependent.
Wu, Juan; Li, ZhengXiang; Wu, PuXun; Yu, HongWei
Constrains on f(T) gravity with the strong gravitational lensing data
NASA Astrophysics Data System (ADS)
Strong lensing is an effective way to probing the properties of dark energy. In this paper, we use the strong lensing data to constrain the f(T) theory, which is a new modified gravity to explain the present accelerating cosmic expansion without the need of dark energy. In our discussion, the CMB and BAO data are also added to constrain model parameters tightly and three different f(T) models are studied. We find that strong lensing has an important role on constraining f(T) models, and once the CMB+BAO data is added, a tighter constraint is obtained. However, the consistency of our result with what is obtained from SNIa+CMB+BAO is actually model-dependent.
Wu, Juan; Li, ZhengXiang; Wu, PuXun; Yu, HongWei
Background Sky Obscuration by Cluster Galaxies as a Source of Systematic Error for Weak Lensing
NASA Astrophysics Data System (ADS)
Lensing magnification and lensing shear measurements of galaxy clusters rely on an accurate determination of the density of background galaxies behind the cluster. The dependence is indirect for shear (via photometric redshift correction schemes) but direct for magnification. Both of these calculations assume a full view of the background sky, but in fact some fraction of the background sky is obscured by the cluster galaxies themselves. We discuss the size of this effect for several current and upcoming cosmological surveys and forecast its impact on cluster mass determinations.
Simet, Melanie; Mandelbaum, Rachel
Using galaxy-galaxy weak lensing measurements to correct the finger of God
NASA Astrophysics Data System (ADS)
For decades, cosmologists have been using galaxies to trace the large-scale distribution of matter. At present, the largest source of systematic uncertainty in this analysis is the challenge of modelling the complex relationship between galaxy redshift and the distribution of dark matter. If all galaxies sat in the centres of haloes, there would be minimal finger-of-God (FoG) effects and a simple relationship between the galaxy and matter distributions. However, many galaxies, even some of the luminous red galaxies (LRGs), do not lie in the centres of haloes. Because the galaxy-galaxy lensing is also sensitive to the off-centred galaxies, we show that we can use the lensing measurements to determine the amplitude of this effect and to determine the expected amplitude of FoG effects. We develop an approach for using the lensing data to model how the FoG suppresses the power spectrum amplitudes and show that the current data imply a 30 per cent suppression at wavenumber k = 0.2 h Mpc-1. Our analysis implies that it is important to complement a spectroscopic survey with an imaging survey with sufficient depth and wide field coverage. Joint imaging and spectroscopic surveys allow a robust, unbiased use of the power spectrum amplitude information: it improves the marginalized error of growth rate fg? d ln D/d ln a by up to a factor of 2 over a wide range of redshifts z < 1.4. We also find that the dark energy equation-of-state parameter, w0, and the neutrino mass, f?, can be unbiasedly constrained by combining the lensing information, with an improvement of 10-25 per cent compared to a spectroscopic survey without lensing calibration.
Hikage, Chiaki; Takada, Masahiro; Spergel, David N.
Algorithm for the direct reconstruction of the dark matter correlation function from weak lensing and galaxy clustering
The clustering of matter on cosmological scales is an essential probe for studying the physical origin and composition of our Universe. To date, most of the direct studies have focused on shear-shear weak lensing correlations, but it is also possible to extract the dark matter clustering by combining galaxy-clustering and galaxy-galaxy-lensing measurements. In order to extract the required information, one must relate the observable galaxy distribution to the underlying dark matter distribution. In this study we develop in detail a method that can constrain the dark matter correlation function from galaxy clustering and galaxy-galaxy-lensing measurements, by focusing on the correlation coefficient between the galaxy and matter overdensity fields. Our goal is to develop an estimator that maximally correlates the two. To generate a mock galaxy catalogue for testing purposes, we use the halo occupation distribution approach applied to a large ensemble of N-body simulations to model preexisting SDSS luminous red galaxy sample observations. Using this mock catalogue, we show that a direct comparison between the excess surface mass density measured by lensing and its corresponding galaxy clustering quantity is not optimal. We develop a new statistic that suppresses the small-scale contributions to these observations and show that this new statistic leads to a cross-correlation coefficient that is within a few percent of unity down to 5h{sup -1} Mpc. Furthermore, the residual incoherence between the galaxy and matter fields can be explained using a theoretical model for scale-dependent galaxy bias, giving us a final estimator that is unbiased to within 1%, so that we can reconstruct the dark matter clustering power spectrum at this accuracy up to k{approx}1h Mpc{sup -1}. We also perform a comprehensive study of other physical effects that can affect the analysis, such as redshift space distortions and differences in radial windows between galaxy clustering and weak lensing observations. We apply the method to a range of cosmological models and explicitly show the viability of our new statistic to distinguish between cosmological models.
Baldauf, Tobias; Smith, Robert E. [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Seljak, Uros [Institute for Theoretical Physics, University of Zurich, Zurich (Switzerland); Physics Department, Astronomy Department and Lawrence Berkeley National Laboratory, University of California, Berkeley, California (United States); Ewha University, 11-1 Daehyun-Dong Seodaemun-Gu Seoul 120-750 (Korea, Republic of); Mandelbaum, Rachel [Department of Astrophysical Sciences, Princeton University, Peyton Hall, Princeton, New Jersey (United States)
Implications for gravitational lensing and the dark matter content in clusters of galaxies from spatially resolved x-ray spectra
NASA Technical Reports Server (NTRS)
A simple method for deriving well-behaved temperature solutions to the equation of hydrostatic equilibrium for intracluster media with X-ray imaging observations is presented and applied to a series of generalized models as well as to observations of the Perseus cluster and Abell 2256. In these applications the allowed range in the ratio of nonbaryons to baryons as a function of radius is derived, taking into account the uncertainties and crude spatial resolution of the X-ray spectra and considering a range of physically reasonable mass models with various scale heights. Particular attention is paid to the central regions of the cluster, and it is found that the dark matter can be sufficiently concentrated to be consistent with the high central mass surface densities for moderate-redshift clusters from their gravitational lensing properties.
Loewenstein, M.
Optical Gravitational Lensing Experiment Cepheids Have Lower Amplitudes in the Small Magellanic Cloud than in the Large Magellanic Cloud.
We selected Cepheids from the Optical Gravitational Lensing Experiment database for the Magellanic Clouds in the period range of 101.1=P=101.4 days. There were 33 objects in the LMC and 35 in the SMC. We find that the median amplitude of Cepheids in the LMC is 18% larger than in the SMC, a 4 sigma effect. For a sample of 42 galactic Cepheids in the same period range, the median amplitude is 7% larger than in the LMC, suggesting that the higher the metal content the larger the amplitude. This implies that the period-flux amplitude relation is not universal and cannot be used to measure distances accurately, unless properly calibrated. PMID:10770700
Paczyński; Pindor
Weak equivalence principle for self-gravitating bodies: A sieve for purely metric theories of gravity
NASA Astrophysics Data System (ADS)
We propose the almost-geodesic motion of self-gravitating test bodies as a possible selection rule among metric theories of gravity. Starting from a heuristic statement, the "gravitational weak equivalence principle," we build a formal operative test able to probe the validity of the principle for any metric theory of gravity in an arbitrary number of spacetime dimensions. We show that, if the theory admits a well-posed variational formulation, this test singles out only the purely metric theories of gravity. This conclusion reproduces known results in the cases of general relativity (as well as with a cosmological constant term) and scalar-tensor theories, but extends also to debated or unknown scenarios, such as the f(R) and Lanczos-Lovelock theories. We thus provide new tools going beyond the standard methods, where the latter turn out to be inconclusive or inapplicable.
Di Casola, Eolo; Liberati, Stefano; Sonego, Sebastiano