The Chemistry of Galaxy Clusters

From X-ray observations of galaxy clusters one derives the mass of the intracluster medium along with its chemical composition. Optical/infrared observations are used to estimate the mass of the stellar components of galaxies, along with their chemical composition and age. This review shows that when combining all this information, several interesting inferences can be drawn, including: (1) galaxies lose more metals than they retain; (2) clusters and the general field have converted the same fraction of baryons into stars, hence the metallicity of the $z = 0$ Universe as a whole has to be nearly the same we see in clusters, $\sim$1/3 solar; (3) for the same reason, the thermal content of the intergalactic medium is expected to be nearly the same as the preheating energy of clusters; (4) a strong increase of the Type Ia supernova (SN) rate with lookback time is predicted if SNe Ia produce a major fraction of cosmic iron; (5) the global metallicity of the $z\approx 3$ Universe was already $\sim$1/10 solar; and (6) the Milky Way disk formed out of material that was pre-enriched to $\sim$1/10 solar by the bulge stellar population.