astro-ph

# Title: Cosmic growth rate measurements from Tully-Fisher peculiar velocities

Abstract: Peculiar velocities are an important probe of the growth rate of structure in the Universe, directly measuring the effects of gravity on the largest scales and thereby providing a test for theories of gravity. Complete peculiar velocity datasets comprise both galaxy redshifts and redshift-independent distance measures, estimated by methods such as the Tully-Fisher relation. Traditionally, the Tully-Fisher relation is first calibrated using distance indicators such as Cepheid variables in a small sample of galaxies; the calibrated relation is then used to determine peculiar velocities. In this analysis, we employ a one-step Bayesian method to simultaneously determine the parameters of the Tully-Fisher relation and the peculiar velocity field. We have also generalised the Tully-Fisher relation by allowing for a curvature at the bright end. We design a mock survey to emulate the Cosmicflows-4 (CF4) peculiar velocity dataset. We then apply our method to the CF4 data to obtain new constraints for the growth rate of structure parameter ($\beta=0.40\pm0.07$), the residual bulk flow ($\mathbf{V}_{\textrm{ext}} =$[69$\pm$15,$-$158$\pm$9,14$\pm$7]\,km$~s^{-1}$ in Supergalactic coordinates), and the parameters for a Tully-Fisher relation with curvature. We obtain an estimate for the product of the growth rate and mass fluctuation amplitude $f\sigma_{8}=0.40\pm0.07$. We combine this measurement of $f\sigma_{8}$ with those of other galaxy redshift surveys to fit the growth index $\gamma$. Assuming cosmological parameters from the latest Planck CMB results, we find that $\gamma>6/11$ is favoured. We plan to use this improved method for recovering peculiar velocities on the large new samples of Tully-Fisher data from surveys such as WALLABY, resulting in more precise growth rate measurements at low redshifts.
 Comments: Submitted to MNRAS Subjects: Cosmology and Nongalactic Astrophysics (astro-ph.CO); Astrophysics of Galaxies (astro-ph.GA) Cite as: arXiv:2301.12648 [astro-ph.CO] (or arXiv:2301.12648v1 [astro-ph.CO] for this version)

## Submission history

From: Paula Boubel [view email]
[v1] Mon, 30 Jan 2023 04:06:37 GMT (6945kb,D)

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