Intermediate‐Element Abundances in Galaxy Clusters

We present the average abundances of the intermediate elements obtained byperforming a stacked analysis of all the galaxy clusters in the archive of theX-ray telescope ASCA. We determine the abundances of Fe, Si, S, and Ni as afunction of cluster temperature (mass) from 1--10 keV, and place strong upperlimits on the abundances of Ca and Ar. In general, Si and Ni are overabundantwith respect to Fe, while Ar and Ca are very underabundant. The discrepancybetween the abundances of Si, S, Ar, and Ca indicate that the alpha-elements donot behave homogeneously as a single group. We show that the abundances of themost well-determined elements Fe, Si, and S in conjunction with recenttheoretical supernovae yields do not give a consistent solution for thefraction of material produced by Type Ia and Type II supernovae at anytemperature or mass. The general trend is for higher temperature clusters tohave more of their metals produced in Type II supernovae than in Type Ias. Theinconsistency of our results with abundances in the Milky Way indicate thatspiral galaxies are not the dominant metal contributors to the intraclustermedium (ICM). The pattern of elemental abundances requires an additional sourceof metals beyond standard SNIa and SNII enrichment. The properties of this newsource are well matched to those of Type II supernovae with very massive,metal-poor progenitor stars. These results are consistent with a significantfraction of the ICM metals produced by an early generation of population IIIstars.Comment: 18 pages, 11 figures, 7 tables. Submitted to Ap