We study the evolution of groups and clusters of galaxies in a Ω = 1, h = 0.5, Λ = 0, CDM scenario using numerical simulations normalized to δM/M = 1. We construct models for galaxy formation assuming instantaneous cooling of gas and the related formation of galaxies in local high-density regions. We compute models that inhibited galaxy formation when the corresponding galactic halo is embedded in a greater cloud for which its cooling time exceeds its crossing time. In these models we find a significant reduction of galaxy formation efficiency in large galactic systems. Mergers of galaxies are taken into account using suitable cross sections and a binding energy criterion. We find that about ∼ 10% of the galaxies have undergone mergers at the present time. We have implemented simple models that consider the effects of energy input by supernovae winds. We find that these effects provide a successful fit to the observed Tully-Fisher relation. We have considered gas infall in systems of galaxies and the effects of supernova winds in the intracluster medium in order to account for the observed gas-to-stars mass ratio Mgas/Mstars as a function of temperature. Although we find a negligible amount of gas infall (<10%), the models allow significant gas mass loss due to supernova winds in small clusters which would explain their high observed galaxy formation efficiency. We have analyzed the spatial distribution of galaxies and their peculiar velocity field in the models. Only when a moderate suppression of galaxy formation in dense environments is considered, is the galaxy-galaxy spatial correlation function consistent with observations. We find no significant velocity bias of the galaxies with respect to the dark matter in any model. This results suggest that the observed galaxy peculiar velocity field put strong constraints to the amplitude of the primordial mass fluctuations in the cosmological models.
Áreas temáticas de ASJC Scopus
- Astronomía y astrofísica
- Ciencias planetarias y espacial