The SmallScale Velocity Dispersion of Galaxies: A Comparison of Cosmological Simulations
Abstract
The velocity dispersion of galaxies on small scales (r ~ 1 h^{1} Mpc), σ_{12}(r), can be estimated from the anisotropy of the galaxygalaxy correlation function in redshift space (Davis & Peebles). We apply this technique to ``mock catalogs'' extracted from Nbody simulations of several different variants of cold dark matterdominated cosmological models, including models with cold + hot dark matter, to obtain results that may be compared consistently with similar results from observations. We find a large variation in the value of σ_{12}(1 h^{1} Mpc) in different regions of the same simulation. We investigate the effects of removing clusters from the simulations, using an automated clusterremoving routine, and find that this reduces the sky variance but also reduces the discrimination between models. However, studying σ_{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 compute the pairwise velocity dispersion directly, in order to check the DavisPeebles method, and find agreement of better than 20% in all the models studied. We also calculate the mean streaming velocity and the pairwise peculiar velocity distribution in the simulations, and compare these with the models used in the DavisPeebles method. We find that the model for the mean streaming velocity may be a substantial source of error in the calculation of σ_{12}.
 Publication:

The Astrophysical Journal
 Pub Date:
 April 1997
 DOI:
 10.1086/303900
 arXiv:
 arXiv:astroph/9604051
 Bibcode:
 1997ApJ...479..606S
 Keywords:

 Cosmology: Theory;
 Galaxies: Clusters: General;
 Galaxies: Distances and Redshifts;
 Cosmology: LargeScale Structure of Universe;
 Astrophysics
 EPrint:
 20 pages, uuencoded (Latex file + 8 Postscript figures), uses AAS macros