The [a/Fe]-[Fe/H] relation in the E-MOSAICS simulations: its connection to the birth place of globular clusters and the fraction of globular cluster field stars in the bulge
The [a/Fe]-[Fe/H] relation in the E-MOSAICS simulations: its connection to the birth place of globular clusters and the fraction of globular cluster field stars in the bulge
复制标题
E-MOSAICS模拟中的[a/Fe]-[Fe/H]关系：它与球状星团诞生地以及球状星团场恒星在核球中的比例的联系
DOI：
10.1093/mnras/stz3341
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发表时间：
2020
影响因子：
4.8
通讯作者：
Hughes M
中科院分区：
文献类型：
--
作者：
Hughes M
球状星团（GC）和星系的场星星群体的α元素丰度编码了关于这些组成部分中每一个的形成的信息。利用E-MOSAICS宇宙学模拟方法，研究了25个银河系质量星系中场星和GC的[α/Fe]-[Fe/H]分布。GCs的[α/Fe]-[Fe/H]分布基本上与场星的分布一致，因此也可以作为星系[α/Fe]-[Fe/H]演化的示踪物。由于它们的星星形成历史的不同，与恒星流（即最近被吸积的）相关的GC在固定的[Fe/H]下系统地降低[α/Fe]。因此，如果观察到GC的[Fe/H]的[α/Fe]较低，则该GC最近与矮星系一起吸积的可能性增加。场星星[α/Fe]-[Fe/H]分布的形状有很大的范围，其中一个显著的星系子集呈现双峰分布，其中高[α/Fe]序列主要由凸出部分的恒星组成，其中很大一部分来自破裂的GC。我们计算了25个模拟星系的凸起部分的破坏GC的贡献，并找到0.3%和14%之间的值，这部分与星系的形成时间相关。这些分数的上限范围与银河系的观测推断测量值是一致的，这表明在这方面银河系不是典型的L* 星系，在早期经历了一个异常快速的增长阶段。
The α-element abundances of the globular cluster (GC) and field star populations of galaxies encode information about the formation of each of these components. We use the E-MOSAICS cosmological simulations of ∼L* galaxies and their GCs to investigate the [α/Fe]–[Fe/H] distribution of field stars and GCs in 25 Milky Way–mass galaxies. The [α/Fe]–[Fe/H] distribution of GCs largely follows that of the field stars and can also therefore be used as tracers of the [α/Fe]–[Fe/H] evolution of the galaxy. Due to the difference in their star formation histories, GCs associated with stellar streams (i.e. which have recently been accreted) have systematically lower [α/Fe] at fixed [Fe/H]. Therefore, if a GC is observed to have low [α/Fe] for its [Fe/H] there is an increased possibility that this GC was accreted recently alongside a dwarf galaxy. There is a wide range of shapes for the field star [α/Fe]–[Fe/H] distribution, with a notable subset of galaxies exhibiting bimodal distributions, in which the high [α/Fe] sequence is mostly comprised of stars in the bulge, a high fraction of which are from disrupted GCs. We calculate the contribution of disrupted GCs to the bulge component of the 25 simulated galaxies and find values between 0.3 and 14 per cent, where this fraction correlates with the galaxy’s formation time. The upper range of these fractions is compatible with observationally inferred measurements for the Milky Way, suggesting that in this respect the Milky Way is not typical of L*galaxies, having experienced a phase of unusually rapid growth at early times.