Mathematics – Logic
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994apj...429...29t&link_type=abstract
The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 429, no. 1, p. 29-35
Mathematics
Logic
2
Astronomical Models, Cosmology, Dark Matter, Galactic Clusters, Galactic Evolution, Computerized Simulation, Galactic Halos, Mass Distribution, Spatial Distribution, Star Formation Rate, Velocity Distribution
Scientific paper
We study the evolution of groups and clusters of galaxies in a Omega = 1, h = 0.5, Lambda = 0, cold dark matter (CDM) scenario using numerical simulations normalized to delta M/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 approximately 10% of the galaxies have undergone mergers at the present time. We have implemented simple models that consider the effects input by supernovae winds. We find that these effects provide a succesful fit to the observed Tully-Fisher relation. We have considered gas infall in systems of galaxies and the efects 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 (less than 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.
Abadi Mario G.
Lambas Diego G.
Tissera Patricia Beatriz
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