标题： 贫金属球状星团及其宿主星系的形成 显示英文标题

标题： Metal-Poor Globular Clusters and the Formation of Their Host Galaxies

摘要： 我们已经确定了八个旋涡星系和早型星系中蓝色、贫金属球状星团（GCs）的总数和特定频率。这些数据，加上文献中的五项测量结果，显示出随着宿主星系质量的增加，蓝色GC特定频率呈上升趋势。这种增加在简单的星系形成模型中无法解释，该模型认为椭圆星系及其GC系统是由典型旋涡星系的合并形成的。这些数据大致与分层形成情景一致，在这种情景中，贫金属GC是在宇宙早期星系组装的初始阶段在一个有限时期内形成的。在这种图景中，观测到的趋势与偏倚有关，即今天的更大质量星系更早开始组装，因此在此贫金属GC形成的早期时期相对形成了更多的GC。我们讨论了如何将观测到的贫金属GC特定频率与模型计算进行比较，以限制这些天体的形成红移。 显示英文摘要

摘要： We have determined the total numbers and specific frequencies of blue, metal-poor globular clusters (GCs) in eight spiral and early-type galaxies. These data, along with five measurements from the literature, show a trend of increasing blue GC specific frequency with increasing mass of the host galaxy. The increase is not accounted for in a simple galaxy formation model in which ellipticals and their GC systems are formed by the merger of typical spiral galaxies. The data appear broadly consistent with hierarchical formation scenarios in which metal-poor GCs are formed over a finite period in the early Universe during the initial stages of galaxy assembly. In this picture, the observed trend is related to biasing, in the sense that the more massive galaxies of today began assembling earlier and therefore formed relatively more GCs during this early epoch of metal-poor GC formation. We discuss how comparisons of the observed specific frequency of metal-poor GCs with model calculations can constrain the formation redshift of these objects.