Enrichment of the Intracluster Medium

The relevance of galaxies of different luminosity and mass for the chemical enrichment of the intracluster medium (ICM) is analysed. For this purpose, I adopt the composite luminosity function of cluster galaxies from Trentham (1998), which exhibits a significant rise at the very faint end. The model - adopting a universal Salpeter IMF - is calibrated on reproducing the M_Fe/L_tot, M_Fe/M_*, and alpha/Fe ratios observed in clusters. Although the contribution to total luminosity and ICM metals peaks around L* galaxies (M* approx -20), faint objects with M_B>-18 still provide at least 30 per cent of the metals present in the ICM. In consistency with the solar alpha/Fe ratios determined by {ASCA}, the model predicts that 60 per cent of the ICM iron comes from Type Ia supernovae. The predicted slope of the relation between intracluster gas mass and cluster luminosity emerges shallower than the observed one, indicating that the fraction of primordial gas increases with cluster richness.