X-ray Observations of the Chemical Abundances in the Intra-Cluster Medium

Abstract: Clusters of galaxies as the largest clearly defined objects in our Universe are ideal laboratories to study the distribution of the most abundant chemical elements heavier than hydrogen and helium and the history of their production. The cluster environment allows us to study the element abundances not only inside the galaxies, but also in the intergalactic space, the intracluster medium. Since the intracluster medium is heated to temperatures of several ten Million degrees, we can study the chemical composition of this medium through X-ray spectroscopy. Up to 13 heavy elements have been detected by X-ray spectroscopy so far. The element most easily detected in the X-ray spectra is iron. In massive galaxy clusters we find a larger mass of heavy elements in the intracluster medium than in the galaxies. The consideration of the intracluster medium is therefore vital for an understanding of the complete history of nucleosynthesis of the heavy elements. The observed abundances for all elements heavier than nitrogen can roughly be modeled by using two types of sources: core collapse supernovae and supernovae type Ia. So called cool-core galaxy clusters show a larger heavy element abundance in the cluster center which seems to be enriched primarily by products of supernovae of type Ia. The evidence for observations of an evolution of the heavy element abundance with redshift has still a moderate significance.