HALOS AND CLUSTERS OF GALAXIES IN SPATIALLY FLAT COLD DARK-MATTER UNIVERSES - VELOCITY FUNCTION AND ANGULAR-MOMENTUM DISTRIBUTION

We have studied the velocity functions and angular momentum distributi on of halos and clusters identified from large N-body simulations in s patially flat cold dark-matter universes. They were compared with prev ious numerical results in much lower spatial resolution or with an ana lytic prediction based on the Press-Schechter theory. We found that al though our simulations reproduce the velocity functions in reasonable agreement with the Press-Schechter theory, there exists a small, but s ystematic, deviation from the formula, particularly for low-density CD M models. Quantitative comparison of our velocity functions with the a vailable observational data revealed that only the standard CDM model with a high biasing parameter of b similar to 2 is consistent with the observation; other CDM models, especially low-density variants, are i n conflict. The distribution of the dimensionless angular momentum (la mbda) is very broad, 0.01 less than or similar to lambda less than or similar to 0.1, and the functional form of the distribution looks very universal, and is quite insensitive to both the cosmological paramete rs and the fluctuation spectrum shape. Although the spatial distributi on of the angular momentum does not show any noticeable correlation of the orientation, halos with relatively small lambda preferentially cl uster around dense regions, which can be interpreted to be consistent with the observed morphology-density relation of galaxies.