Distant clusters of galaxies: X-ray properties and their relations

Abstract

We investigate the evolution of clusters of galaxies in a sample of distant clusters with redshifts between 0.3 and 1.0. We show the abilities and limitations of combined ROSAT and ASCA data to draw cosmological conclusions. For the first time bolometric luminosities, masses, gas masses, gas mass fractions, and iron masses are derived in such a distant sample in a consistent way. We compare these quantities with the corresponding quantities in nearby samples. Furthermore, we analyse relations between these quantities and the gas temperature, metallicity and the morphological parameters and compare them with relations in nearby samples. Fits to all relations with power law functions are given. We find relations between X-ray luminosity, temperature, mass, gas mass, core radius and beta, similar to those found in nearby clusters. Furthermore, we find gas mass fractions increasing with radius, with the effect being stronger in less massive clusters. Within errors we find no evidence for evolution in any of the quantities nor in any of the relations. These results favour a low Omega universe, but without strong constraints. We point out how promising the next generation of X-ray satellites XMM, CHANDRA and ASTRO-E are for cosmological studies with clusters. From the new observations primarily two measurements are required: detection of more distant clusters and measurements of the spectral and spatial parameters with much higher precision.