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Star cluster survival in dark matter haloes: an old cluster in Eridanus II?
Monthly Notices of the Royal Astronomical Society ( IF 4.7 ) Pub Date : 2021-05-08 , DOI: 10.1093/mnras/stab1322
Jairo A Alzate 1 , Verónica Lora 1 , Gustavo Bruzual 1 , Luis Lomelí-Núñez 2 , Bernardo Cervantes Sodi 1
Affiliation  

The star formation history and the internal dynamics of Milky Way satellite galaxies are often complicated. In the last years, a substantial fraction of the known faint dwarf satellites have been studied. Some of them show embedded stellar substructures, such as star clusters and even globular star clusters. In this work, we study Eridanus II, a dwarf spheroidal satellite that hosts a star cluster, using published and archival data from the Hubble Space Telescope Advanced Camera for Surveys. We employ a Bayesian hierarchical method to infer the star formation history of Eridanus II. We find that the bulk of the stars in Eridanus II are very old ($13.5_{-1}^{+0.5}$ Gyr) and quite metal-poor (Z = 0.000 01). We do not find any evidence of the presence of an intermediate age or young population in Eri II. We cannot date the embedded star cluster as a separate entity, but we find it likely that the cluster has a similar age and metallicity as the bulk of the stars in Eri II. The existence of an old star cluster in a dark matter dominated old metal-poor dwarf galaxy is of major importance to cast light on the dark matter distribution within dwarf galaxies. The existence of intermediate age stars is required by the recent detection of carbon stars in Eri II. Since no recent star formation is detected, blue-straggler fusions of lower mass stars are the most likely origin of the carbon star progenitors.

中文翻译:

暗物质晕中的星团生存:波江座 II 中的旧星团?

银河系卫星星系的恒星形成历史和内部动力学往往很复杂。在过去的几年里,已经研究了相当大一部分已知的微弱矮卫星。其中一些显示出嵌入的恒星子结构,例如星团甚至球状星团。在这项工作中,我们使用来自哈勃太空望远镜高级巡天相机的已发布和存档数据研究了波江座 II,这是一颗拥有星团的矮球状卫星。我们采用贝叶斯分层方法来推断波江座 II 的恒星形成历史。我们发现波江座 II 中的大部分恒星都非常古老($13.5_{-1}^{+0.5}$ Gyr)并且金属含量很低(Z = 0.000 01)。我们没有发现任何证据表明 Eri II 中存在中年或年轻人。我们无法确定嵌入星团作为一个单独实体的日期,但我们发现该星团的年龄和金属丰度可能与 Eri II 中的大部分恒星相似。在暗物质占主导地位的旧金属贫乏矮星系中存在一个旧星团对于揭示矮星系内的暗物质分布具有重要意义。最近在 Eri II 中发现碳星需要中龄恒星的存在。由于没有检测到最近的恒星形成,低质量恒星的蓝色散乱融合是碳恒星前身最可能的起源。在暗物质占主导地位的旧金属贫乏矮星系中存在一个旧星团对于揭示矮星系内的暗物质分布具有重要意义。最近在 Eri II 中发现碳星需要中龄恒星的存在。由于没有检测到最近的恒星形成,低质量恒星的蓝色散乱融合是碳恒星前身最可能的起源。在暗物质占主导地位的旧金属贫乏矮星系中存在一个旧星团对于揭示矮星系内的暗物质分布具有重要意义。最近在 Eri II 中发现碳星需要中龄恒星的存在。由于没有检测到最近的恒星形成,低质量恒星的蓝色散乱融合是碳恒星前身最可能的起源。
更新日期:2021-05-08
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