Title: Constraints on neutrino masses from Lyman-alpha forest power spectrum with BOSS and XQ-100,
Abstract: We present constraints on masses of active and sterile neutrinos. We use the
one-dimensional Ly$\alpha$-forest power spectrum from the Baryon Oscillation
Spectroscopic Survey (BOSS) of the Sloan Digital Sky Survey (SDSS-III) and from
the VLT/XSHOOTER legacy survey (XQ-100). In this paper, we present our own
measurement of the power spectrum with the publicly released XQ-100 quasar
spectra.
Fitting Ly$\alpha$ data alone leads to cosmological parameters in excellent
agreement with the values derived independently from Planck 2015 Cosmic
Microwave Background (CMB) data. Combining BOSS and XQ-100 Ly$\alpha$ power
spectra, we constrain the sum of neutrino masses to $\sum m_\nu < 0.8$ eV (95\%
C.L). With the addition of CMB data, this bound is tightened to $\sum m_\nu <
0.14$ eV (95\% C.L.).
With their sensitivity to small scales, Ly$\alpha$ data are ideal to
constrain $\Lambda$WDM models. Using XQ-100 alone, we issue lower bounds on
pure dark matter particles: $m_X \gtrsim 2.08 \: \rm{keV}$ (95\% C.L.) for
early decoupled thermal relics, and $m_s \gtrsim 10.2 \: \rm{keV}$ (95\% C.L.)
for non-resonantly produced right-handed neutrinos. Combining the 1D Ly$\alpha$
forest power spectrum measured by BOSS and XQ-100, we improve the two bounds to
$m_X \gtrsim 4.17 \: \rm{keV}$ and $m_s \gtrsim 25.0 \: \rm{keV}$ (95\% C.L.).
The $3~\sigma$ bound shows a more significant improvement, increasing from $m_X
\gtrsim 2.74 \: \rm{keV}$ for BOSS alone to $m_X \gtrsim 3.10 \: \rm{keV}$ for
the combined BOSS+XQ-100 data set.
Finally, we include in our analysis the first two redshift bins ($z=4.2$ and
$z=4.6$) of the power spectrum measured with the high-resolution HIRES/MIKE
spectrographs. The addition of HIRES/MIKE power spectrum allows us to further
improve the two limits to $m_X \gtrsim 4.65 \: \rm{keV}$ and $m_s \gtrsim 28.8
\: \rm{keV}$ (95\% C.L.).