Galaxy Mergers in a CDM Model

A particle code is used to follow the evolution of a Cold Dark Matter spectrum in an Ω = 1 background, treating half of the 524288 particles as a gas that can cool and turn into stars. The number density of galaxies as a function of redshift is well fit by the BBKS peaks statistics, using a sharp threshold having a normalized overdensity νt = 1.44(l + z)/σ0(M), where σ0(M) is the linear extrapolation of the initial RMS density fluctuation on mass scale M. The dark halo number density-redshift relation is fit with the same νt using the volume averaging Press-Schechter model. The merger rates of the model galaxies are compared to observational estimates.