18 February 2020A first approach toward galaxy peculiar velocities at redshift z~0.1

Peculiar motion introduces systematic variations in the observed luminosity distribution of galaxies. This allows one to measure cosmological bulk flows and to reconstruct the peculiar velocity field from large galaxy redshift surveys using standard techniques based on maximum-likelihood estimation. Thus the approach is independent of galaxy bias and traditional distance indicators which are prone to systematic errors. Using the NYU-VAGC based on the SDSS DR7 data release, we apply this method to estimate the cosmological bulk flow out to a depth of around 400 Mpc/h. Including higher-order moments and using the corresponding posterior likelihood, we further attempt to constrain the (angular) velocity power spectrum in different redshift bins and to measure cosmological parameters such as sigma_8 directly from the SDSS data. Finally, we discuss the prospects of this and similar approaches in the context of next-generation surveys.