HEAO A-1 Observations of X-Ray Emitting Clusters of Galaxies.

Clusters of galaxies have been known to be sources of X-ray emission since 1966. Statistical analysis of how the X-ray emission from clusters of galaxies is related to other cluster properties has been limited by the small number of clusters observed in the X-ray region and the completeness of the X-ray sample being considered. This study solves both of these limitations by producing a flux -limited catalog of X-ray emitting Abell clusters of galaxies and using this catalog to investigate how the X-ray emission correlates with other cluster properties. X-ray data from the HEAO A-1 experiment were used to search for X-ray emission from Abell clusters of galaxies. Selection criteria were chosen to ensure that the resulting catalog was complete and as free as possible from selection effects. The resulting identifications and X-ray luminosities were used to check correlations with other cluster properties. Special consideration was given to observational selection effects and consistency checks. The data were consistent with all clusters of galaxies being X-ray emitters beyond some limiting luminosity, which depends on cluster richness. Furthermore, the X -ray luminosity of clusters is correlated with the richness of the cluster, its galaxy content, and the spatial distribution and galaxy content of galaxies within the cluster. It is concluded that the X-ray emission from clusters of galaxies depends not only on the richness of the cluster but also the morphology of the cluster.