Mergers and bias in a cold dark matter cosmology

Abstract

A dissipative N-body code is used to follow the evolution of a cold dark matter spectrum in an Omega = 1, h = 0.5 background. The star and galaxy formation in boxes of three different sizes is shown, and the relative degrees of clustering of dark matter, halos, and galaxies is discussed and used to normalize to the current epoch. The streaming velocities of the galaxies and dark matter are measured and compared with linear theory. The pairwise velocities of the galaxies and dark matter are studied and used with estimates of galactic merger rates to discuss the role that mergers play in galaxy formation. The number density-redshift relation of galaxies is shown to be well described by the statistical description of density perturbation peaks by Bardeen et al. (1986), whereas halos are better fitted by the volume-averaging, hierarchical model of Press and Schechter (1974). The model galaxies exhibit only a modest enhancement of their two-point correlation function over that of the dark matter.