COLD DARK-MATTER .2. SPATIAL AND VELOCITY STATISTICS

We examine high-resolution gravitational N-body simulations of the Ome ga = 1 cold dark matter (CDM) model in order to determine whether ther e is any normalization of the initial density fluctuation spectrum tha t yields acceptable results for galaxy clustering and velocities. Dens e dark matter halos in the evolved mass distribution are identified wi th luminous galaxies; the most massive halos are also considered as si tes for galaxy groups, with a range of possibilities explored for the group mass-to-light ratios. We verify the earlier conclusions of White et al. (1987) for the low-amplitude (high-bias) CDM model-the galaxy correlation function is marginally acceptable but that there are too m any galaxies. We also show that the peak biasing method does not accur ately reproduce the results obtained using dense halos identified in t he simulations themselves. The COBE anisotropy implies a higher normal ization, resulting in problems with excessive pairwise galaxy velocity dispersion unless a strong velocity bias is present. Although we conf irm the strong velocity bias of halos reported by Couchman and Carlber g (1992), we show that the galaxy motions are still too large on small scales. We find no amplitude for which the CDM model can reconcile si multaneously the galaxy correlation function, the low pairwise velocit y dispersion, and the richness distribution of groups and clusters. Wi th the normalization implied by COBE, the CDM spectrum has too much po wer on small scales if Omega = 1.