The Contribution of Population III to the Enrichment and Preheating of the Intracluster Medium

Intracluster medium (ICM) abundances are higher than expected assumingenrichment by supernovae with progenitors belonging to the simple stellarpopulation (SSP) observed in cluster galaxies, if stars formed with a standardinitial mass function (IMF). Moreover, new results on ICM oxygen abundancesimply that nucleosynthesis occurred with nonstandard yields. The hypothesisthat hypernovae (HN) in general, and HN associated with Population III (PopIII) stars in particular, may significantly contribute to ICM enrichment ispresented and evaluated. The observed abundance anomalies can be explained by ahypernovae-producing subpopulation of the SSP, but only if it accounts for halfof all supernova explosions and if Type Ia supernova rates are very low. Also,the implied energy release may be excessive. However, an independent Pop IIIcontribution -- in the form of metal-free, very massive stars that evolve intohypernovae -- can also account for all the observed abundances, while avoidingthese drawbacks and accommodating a normal IMF in subsequent stellargenerations. The required number of Pop III stars provides sufficient energyinjection (at high redshift) to explain the ICM ``entropy floor''. Pop IIIhypernova pre-enrich the intergalactic medium, and can produce a significantfraction of the metals observed in the Lyman-alpha forest. Several testablepredictions for ICM and IGM observations are made.Comment: 15 pages Latex including 1 encapsulated postscript file; ApJ, in pres