Monday, January 20, 2014 - 11:00am
Martin Feix (Technion):
"Approaching peculiar velocities at redshift z∼0.1"
Abstract. Peculiar motion introduces systematic variations in the observed luminosity distribution of galaxies. As recently proposed, this allows one to measure cosmological bulk flows and to reconstruct the peculiar velocity field from large galaxy redshift surveys. Technically, this is achieved by maximizing the probability to estimate a galaxy's absolute magnitude given its observed apparent magnitude and redshift. Thus the approach is independent of galaxy bias and traditional distance indicators, which are prone to systematic errors. Using the NYU value-added galaxy catalog based on the SDSS DR7 data release, we apply this method to measure 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 estimate the (angular) velocity power spectrum in different redshift bins. Finally, we attempt to constrain cosmological parameters such as sigma_8 directly from the SDSS data.