Abstract
We compare (� /Fe), metallicity, and age distributions of globular clusters in elliptical, lenticular, and spiral gal- axies, which we derive from Lick line index measurements. We find a large number of globular clusters in elliptical galaxies that reach significantly higher (� /Fe) values (½� /Fe� > 0:5) than any clusters in lenticular and spiral gal- axies. Most of these extremely � -enriched globular clusters are old (t > 8 Gyr), and cover the metallicity range � 1P ½Z/HP0.Acomparisonwithsupernovayieldmodelssuggeststhattheprogenitorgascloudsofthese globular clustersmusthavebeenpredominantlyenrichedbymassivestars(k20 M� ),withlittlecontributionfromlowermass stars. The measured (� /Fe) ratios are also consistent with yields of very massive pair-instability supernovae (� 130Y190 M� ). Both scenarios imply that the chemical enrichment of the progenitor gas was completed on ex- tremely short timescales of the order of a few Myr. Given the lower (� /Fe) average ratios of the diffuse stellar popu- lation in early-type galaxies, our results suggest that these extremely � -enhanced globular clusters could be members of the very first generation of star clusters formed, and that their formation epochs would predate the formation of the majority of stars in giant early-type galaxies. Subject headingg galaxies: evolution — galaxies: formation — galaxies: star clusters — globular clusters: general
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