We analyze statistical properties of the large-scale distribution of galaxies in numerical simulations of biased cold dark matter (CDM) cosmologies. We explore different schemes for biased galaxy formation assuming a local nature (0.5-3 h-2 Mpc) for the processes that segregate luminous and dark matter. We consider biased and antibiased models for galaxy formation, using simple prescriptions for the assignment of the galaxies from the mass distribution. We also analyze models where galaxy luminosities depend on local density. For all the models where galaxies are more clustered than the dark matter we find that the angular two-point correlation function has not enough power on large angular separations as compared with APM measurements. We find that a luminosity-density dependence cannot modify these negative results. However, we find that antibiased models provide a fair agreement between the angular correlation function of simulations and the observations. Nevertheless, the peculiar velocities of the galaxies in the simulations exceed by a factor of 1.5-2 the observed peculiar velocities of galaxies. Similarly, velocity dispersions of clusters in the simulations are also a factor of 2 larger than the typical velocity dispersion of a rich cluster of galaxies. Taking into account the recent results of COBE experiments, we have analyzed CDM models with δM/M = 1. In order to reproduce in these simulations the observed clustering and velocity distribution of galaxies, we develop a simple model that includes mergers of galaxy pairs in high-density regions. The angular correlation function of this model has more power than that obtained in the Lick catalog on large scales, although it provides only a marginal fit to APM measurements. The reduction of galaxy velocities by mergers generates a rich-cluster velocity dispersion, σ ≃ 1000-1500 km s-1, consistent with observations.
Áreas temáticas de ASJC Scopus
- Astronomía y astrofísica
- Ciencias planetarias y espacial