Pairwise velocities in the halo model: luminosity and scale dependence |
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| Authors: | An&#;e Slosar Uro&#; Seljak Argyro Tasitsiomi |
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| Institution: | Faculty of Mathematics and Physics, University of Ljubljana, Slovenia;International Centre for Theoretical Physics, Trieste, Italy;Department of Physics, Princeton University, Princeton, NJ 08544, USA;Department of Astronomy &Astrophysics, Kavli Institute for Cosmological Physics, The University of Chicago, Chicago, IL 60637, USA |
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| Abstract: | We investigate the properties of the pairwise velocity dispersion as a function of galaxy luminosity in the context of a halo model. We derive the distribution of velocities of pairs at a given separation taking into account both one- and two-halo contributions. We show that pairwise velocity distribution in real space is a complicated mixture of host–satellite, satellite–satellite (sat–sat) and two-halo pairs. The peak value is reached at around 1 h ?1 Mpc and does not reflect the velocity dispersion of a typical halo hosting these galaxies, but is instead dominated by the sat–sat pairs in high-mass clusters. This is true even for cross-correlations between bins separated in luminosity. As a consequence, the velocity dispersion at a given separation can decrease with luminosity, even if the underlying typical halo host mass is increasing, in agreement with recent observations. We compare our findings to numerical simulations and find a good agreement. Numerical simulations also suggest a luminosity-dependent velocity bias, which depends on the subhalo mass. We develop models of the auto- and cross-correlation functions of luminosity subsamples of galaxies in the observable r proj–π space and calculate the inferred velocity dispersion as a function of wavevector if dispersion model is fit to the redshift-space power spectrum. We find that so-derived pairwise velocity dispersion also exhibits a bump at k ～ 1 h Mpc?1 . |
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| Keywords: | large-scale structure of Universe |
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