Galaxy Clusters and the Amplitude of Primordial Fluctuations

TLDR: In this article, the distribution of velocity dispersion, gas temperature, and mass-to-light ratio for Abell clusters are calculated in the standard cold dark matter (CDM) cosmogony in order to test the validity of the hierarchical clustering model for the formation of cosmic structure and to fix the value of the biasing parameter b which quantifies the segregation between galaxies and mass.

Abstract: The distributions of velocity dispersion, gas temperature, and mass-to-light ratio for Abell clusters are calculated here in the standard cold dark matter (CDM) cosmogony in order to test the validity of the hierarchical clustering model for the formation of cosmic structure and to fix the value of the biasing parameter b which quantifies the segregation between galaxies and mass. To compare model predictions with optical data, catalogs of galaxies are constructed from N-body simulations and subjected to projection effects similar to those in Abell's cluster catalog. It is found that a significant fraction of rich clusters identified in projection do not correspond to rich three-dimensional clusters, but result instead from superpositions of foreground groups on poorer clusters. A similar fraction of true rich clusters are missed in the projected catalogs. Combining the simulations with recent hydrodynamical models, it is found that CDM models with b of 2-2.5 provide an acceptable match to present data. 52 refs.