SUPERNOVAE TYPES IA II AND INTRACLUSTER MEDIUM ENRICHMENT/

We re-examine the respective roles played by supernovae (SNe) Types Ia and II in enriching the intracluster medium (ICM) of galaxy clusters in the light of the recent downward shift of the ASCA abundance ratios of alpha-elements to iron favoured by Ishimaru & Arimoto. Because of this shift, Ishimaru & Arimoto conclude that greater than or similar t o 50 per cent of the ICM iron must have originated from within Type Ia SNe progenitors. A point not appreciated in their study, nor in most previous analyses, is the crucial dependence of such a conclusion upon the adopted massive star physics. Employing several alternative Type II SN yield compilations, we demonstrate how uncertainties in the trea tment of convection and mass-loss can radically alter our perception o f the relative importance of Type Ia and II SNe as ICM polluters. If m ass-loss of the form favoured by Maeder or convection of the form favo ured by Arnett is assumed, the effect upon the oxygen yields would lea d us to conclude that Type Ia SNe play no part in polluting the ICM, i n contradiction with Ishimaru & Arimoto. Apparent dichotomies still ex ist (e.g., the mean ICM neon-to-iron ratio implies a similar to 100 pe r cent Type II Fe origin, while the mean sulphur ratio indicates a sim ilar to 100 per cent Type Ia origin) that cannot be reconciled with th e currently available yield tables.