Statistical Properties of X‐Ray Clusters: Analytic and Numerical Comparisons

TLDR

The study compares Eulerian hydrodynamic simulations of cluster formation to virial scaling relations among cluster mass, dark matter velocity dispersion, gas temperature, and luminosity across many clusters at various redshifts in three cosmological models (CDM+HDM, CDM, OCDM). Analytic virial relations accurately reproduce three of the four bulk quantities, and the luminosity relation also matches after a resolution‑correction, with normalizations agreeing closely with previous literature.

Abstract

We compare the results of Eulerian hydrodynamic simulations of cluster formation against virial scaling relations between four bulk quantities: the cluster mass, the dark matter velocity dispersion, the gas temperature, and the cluster luminosity. The comparison is made for a large number of clusters at a range of redshifts in three different cosmological models (cold plus hot dark matter, cold dark matter, and open cold dark matter). We find that the analytic formulae provide a good description of the relations between three of the four numerical quantities. The fourth (luminosity) also agrees once we introduce a procedure to correct for the fixed numerical resolution. We also compute the normalizations for the virial relations and compare extensively to the existing literature, finding remarkably good agreement.