An Aligned Stream of Low-Metallicity Clusters in the Halo of the Milky Way
An Aligned Stream of Low-Metallicity Clusters in the Halo of the Milky Way
复制标题
银河系光环中排列整齐的低金属度星团流
DOI：
10.1126/science.1073090
复制
发表时间：
2002
期刊：
影响因子：
56.9
通讯作者：
Young
中科院分区：
文献类型：
--
作者：
Suk;Young
现代天文学中一个长期存在的问题是银河系球状星团的奇怪划分，即根据天琴座RR恒星的性质进行的Oosterhoff二分法。在这里，我们发现大多数金属丰度最低的([Fe/H]<；-2.0)团簇，对于理解这一现象是必不可少的，它们在外晕中显示出平面排列。这种排列，结合来自运动学和恒星群的证据，表明捕获的起源来自卫星星系。我们表明，与水平分支演化效应一起，产生这种二分性的因素可能是银河系中星系团形成时期与卫星之间的一个很小的时间间隔。这一结果与传统观点相反，传统观点认为，金属贫乏的星系团代表着银河系中土著和最古老的人口。
One of the long-standing problems in modern astronomy is the curious division of Galactic globular clusters, the “Oosterhoff dichotomy,” according to the properties of their RR Lyrae stars. Here, we find that most of the lowest metallicity ([Fe/H] < –2.0) clusters, which are essential to an understanding of this phenomenon, display a planar alignment in the outer halo. This alignment, combined with evidence from kinematics and stellar population, indicates a captured origin from a satellite galaxy. We show that, together with the horizontal-branch evolutionary effect, the factor producing the dichotomy could be a small time gap between the cluster-formation epochs in the Milky Way and the satellite. The results oppose the traditional view that the metal-poorest clusters represent the indigenous and oldest population of the Galaxy.