The Small Scale Velocity Dispersion of Galaxies: A Comparison of Cosmological Simulations

Abstract

The velocity dispersion of galaxies on small scales ($r\sim 1h^{-1}$ Mpc), ${\sigma }_{12}(r)$, can be estimated from the anisotropy of the galaxy-galaxy correlation function in redshift space. We apply this technique to ``mock-catalogs'' extracted from N-body simulations of several different variants of Cold Dark Matter dominated cosmological models to obtain results which may be consistently compared to similar results from observations. We find a large variation in the value of ${\sigma }_{12}(1h^{-1}Mpc)$ in different regions of the same simulation. We conclude that this statistic should not be considered to conclusively rule out any of the cosmological models we have studied. We attempt to make the statistic more robust by removing clusters from the simulations using an automated cluster-removing routine, but this appears to reduce the discriminatory power of the statistic. However, studying ${\sigma }_{12}$ as clusters with different internal velocity dispersions are removed leads to interesting information about the amount of power on cluster and subcluster scales. We also compute the pairwise velocity dispersion directly and compare this to the values obtained using the Davis-Peebles method, and find that the agreement is fairly good. We evaluate the models used for the mean streaming velocity and the pairwise peculiar velocity distribution in the original Davis-Peebles method by comparing the models with the results from the simulations.

20 pages, uuencoded (Latex file + 8 Postscript figures), uses AAS macros

References in corpus (5)

• The Structure of Cold Dark Matter Halos
• Cold Dark Matter Models with a Cosmological Constant
• PAIRWISE VELOCITIES OF GALAXIES IN THE CFA AND SSRS2 REDSHIFT SURVEYS
• The distribution of pairwise peculiar velocities in the nonlinear regime
• Galaxy Tracers and Velocity Bias

Cited by in corpus (10)

• Clustering of Galaxies in a Hierarchical Universe: I. Methods and Results at z=0
• Evolution of structure in cold dark matter universes
• Populating Dark Matter Haloes with Galaxies: Comparing the 2dFGRS with Mock Galaxy Redshift Surveys
• The Dependence of Velocity and Clustering Statistics on Galaxy Properties
• Compact groups in the UZC galaxy sample
• Locally Biased Galaxy Formation and Large Scale Structure
• The Galaxy Pairwise Velocity Dispersion as a Function of Local Density
• The Caltech Faint Galaxy Redshift Survey XII: Clustering of Galaxies
• The Galaxy-Weighted Small-Scale Velocity Dispersion of the Las Campanas Redshift Survey
• Modeling non-linear effects in the redshift space two-point correlation function and its implications for the pairwise velocity dispersion