Department of Astronomy and Space Science, ARCSEC, Sejong University, Seoul 143-747, Korea.
Nature. 2009 Nov 26;462(7272):480-2. doi: 10.1038/nature08565.
The most massive globular cluster in the Milky Way, omega 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 omega Cen, other peculiar globular clusters do not. Therefore omega Cen and M 22 are viewed as exceptional, and the presence of chemical inhomogeneities in other clusters is seen as 'pollution' from the intermediate-mass asymptotic-giant-branch stars expected in normal globular clusters. Here we report Ca abundances for seven globular clusters and compare them to omega 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 omega Cen, are most probably the relics of more massive primeval dwarf galaxies that merged and disrupted to form the proto-Galaxy.
银河系中质量最大的球状星团——半人马座ω，被认为是一个已经瓦解的矮星系的剩余核心，这与分层合并模型的预期相符。它包含了几个恒星群体，它们的重元素丰度不同，这是由超新星提供的——这一过程被称为金属丰度增加。虽然 M 22 似乎与半人马座ω相似，但其他奇特的球状星团并非如此。因此，半人马座ω和 M 22 被视为例外，而其他星团中存在的化学不均匀性则被视为来自正常球状星团中预期的中等质量渐近巨星支恒星的“污染”。在这里，我们报告了七个球状星团的钙丰度，并将其与半人马座ω进行了比较。在这些恒星系统中，只有通过大量大质量恒星的超新星爆炸才能提供钙和其他重元素，但目前这些星团的引力势无法保留这些爆炸的大部分喷出物。我们的结论是，这些球状星团，就像半人马座ω一样，很可能是更庞大原始矮星系的遗迹，这些矮星系合并并瓦解形成了原星系。
