Enrichment by supernovae in globular clusters with multiple populations

摘要

The most massive globular cluster in the Milky Way, ω Centauri, is thought to be the remaining core of a disrupted dwarf galaxy, as expected within the model of hierarchical merging. It contains several stellar populations having different heavy elemental abundances supplied by supernovae-a process known as metal enrichment. Although M 22 appears to be similar to ω Cen, other peculiar globular clusters do not. Therefore to Cen and M 22 are viewed as exceptional, and the presence of chemical inhomogene-ities in other clusters is seen as 'pollution' from the intermediate-mass asymptotic-giant-branch stars expected in normal globular dusters. Here we report Ca abundances for seven globular clusters and compare them to co Cen. Calcium and other heavy elements can only be supplied through numerous supernovae explosions of massive stars in these stellar systems, but the gravitational potentials of the present-day clusters cannot preserve most of the ejecta from such explosions. We conclude that these globular clusters, like ω Cen, are most probably the relics of more massive primeval dwarf galaxies that merged and disrupted to form the proto-Galaxy.%绕银河系运转的球状星团，被认为是我们所掌rn握的最接近于具有统一年龄和相同组成、记录rn了自我们银河系诞生以来恒星演化历史的星rn群。不过，这些星团中最亮的一个“ω Centaruri”rn长期以来被认为是这一趋势的一个例外，它包rn含多个星群，这些星群在铁含量及年龄上相差rn很大。两个小组在本期Nature上报告，他们发rn现了更多含有不同星群的球状星团。Lee等人rn证实了这样一个怀疑：巨型球状星团M22包含rn多个具有不同钙含量的各自截然不同的星群。rn同类星团中几个其他星团也是如此。Ferraro等rn人报告，Terzan 5(“银河系核球”中一个与球rn状星团相似的体系)包含两个具有不同铁含量rn和年龄的星群。这些发现表明，ω Cen、M22、rnTerzan 5和其他相似星团是合并之后最终形成rn银河系的矮星系和其他原始天体的遗迹。