A Comparison of Metal Enrichment Histories in Rich Clusters and Individual Luminous Elliptical Galaxies

Abstract

Hot, X-ray emitting gaseous halos around massive elliptical galaxies are a result of both stellar mass loss and inflow toward the overdensity from which giant ellipticals and their associated galaxy groups formed. The metal abundance in this gas contains important information about early star formation and past supernova activity. We find that Type II supernovae based on a Salpeter IMF, plus a small number of additional Type Ia supernovae, can explain the the density, temperature and abundance profiles currently observed in gaseous halos around massive ellipticals. Within the central, optically bright regions of luminous ellipticals, approximately half of the interstellar iron is produced by Type Ia supernovae and half by mass lost from evolving stars which were originally enriched by Type II supernovae. However, iron and silicon abundances in the intracluster gas within rich clusters suggest enrichment by a larger number of supernovae per unit optical light than we require for massive ellipticals, either more Type Ia or more Type II from a flatter IMF. Since the enrichment histories of massive ellipticals and rich clusters are fundamentally different, E and SO galaxies may not be the only sources of metal enrichment in rich cluster gas.