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arXiv 2009.12423astro-ph.GA
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Milky Way球状星团多个群体中的不同钠增强

Different Sodium enhancements among multiple populations of Milky Way globular clusters

Andrés E. Piatti

备注：
10 pages, 9 figures. Accepted for publication in Astronomy & Astrophysics
发表信息：
A&A 643, A77 (2020)
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摘要：

我们寻找线索，以了解不同的钠丰度测量的第一代和第二代恒星的古老银河系球状星团。为此，我们收集了最近的文献中提到的钠丰度，轨道参数，结构和内部动力学性质和年龄在一个均匀的规模的28个球状星团。我们发现，集群内的Na富集，测量的第一代和第二代恒星之间的Na丰度的差异，表现出一种趋势，作为第一代恒星的Na丰度的函数，在这个意义上，越Na贫的第一代恒星，Na富集更大。利用球状星团轨道的倾角，分析的Na富集也暗示了在~0.3 dex处的边界，以区分具有吸积或原位起源的球状星团，吸积的球状星团具有更大的Na富集。由于在吸积的球状星团中观察到相对较大的星系团内钠增强，而在原位形成的球状星团中观察到较小的钠增强（尽管不是唯一的），我们推测钠富集的幅度可能与构建模块范式有关。球状星团在第一代和第二代恒星形成时，似乎保留了这种分层星系形成过程的记忆。

英文摘要：

We searched for trails to understand the different Na abundances measured in first and second generation stars of ancient Milky Way globular clusters. For that purpose, we gathered from the recent literature the aforementioned Na abundances, orbital parameters, structural and internal dynamical properties and ages in an homogeneous scale of 28 globular clusters. We found that the intra-cluster Na enrichment, measured by the difference of Na abundances between first and second generation stars, exhibits a trend as a function of the Na abundances of first generation stars, in the sense that the more Na-poor the first generation stars, the larger the Na enrichment. By using the inclinations of the globular clusters' orbits, the analyzed Na enrichments also hinted at a boundary at ~0.3 dex to differentiate globular clusters with an accreted or in situ origin, the accreted globular clusters having larger Na enrichments. Because relatively larger intra-cluster Na enhancements are seen in accreted globular clusters, and small Na enhancements are observed in globular clusters formed in situ (although not exclusively), we speculate with the possibility that the amplitude of the Na enrichment could be linked with the building block paradigm. Globular clusters at the time of formation of first and second generation stars would seem to keep memory of this hierarchical galaxy formation process.

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