Fossil stellar streams and their globular cluster populations in the E-MOSAICS simulations
Fossil stellar streams and their globular cluster populations in the E-MOSAICS simulations
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DOI：
10.1093/mnras/sty2889
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发表时间：
2018-10
影响因子：
4.8
通讯作者：
M. Hughes;J. Pfeffer;M. Martig;N. Bastian;R. Crain;J. Kruijssen;M. Reina-Campos
中科院分区：
文献类型：
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作者：
M. Hughes;J. Pfeffer;M. Martig;N. Bastian;R. Crain;J. Kruijssen;M. Reina-Campos
恒星晕编码了星系吸积历史的化石记录，通常以低表面亮度结构的形式存在，例如恒星流。虽然它们的低表面亮度使得确定它们的年龄、金属丰度、运动学和空间结构具有挑战性，但坠落的星系还在晕中沉积了球状星团（GC），这些球状星团很明亮，因此更容易观察和表征。为了了解如何使用与恒星流相关的 GC 来估计恒星质量及其母星系的坠落时间，我们研究了 E-MOSAICS 项目中的 15 个星系及其星团模拟的子集。 E-MOSAICS 是一套流体动力学模拟，包含用于 GC 形成和演化的子网格模型。我们发现，质量更大的吸积星系通常会产生更年轻、更富含金属的GC。这种较低的年龄是由于更大质量的星系中更长的星团形成历史造成的。此外，在固定的恒星质量下，后来吸积的星系拥有更年轻的星团，因为它们可以继续形成GC，而不会更长时间地受到环境影响。这解释了与被认为是在银河系形成历史早期吸积的卫星中形成的星团相比，在银河系晕中与人马座矮星系相关的星团所观察到的年龄范围较大的原因。利用与人马座矮星相关的 GC 的年龄，我们估计维里半径穿越回顾时间（坠落时间）为 $9.3 \pm 1.8 Gyr$。
Stellar haloes encode a fossil record of a galaxy's accretion history, generally in the form of structures of low surface brightness, such as stellar streams. While their low surface brightness makes it challenging to determine their age, metallicity, kinematics and spatial structure, the infalling galaxies also deposit globular clusters (GCs) in the halo, which are bright and therefore easier to observe and characterise. To understand how GCs associated with stellar streams can be used to estimate the stellar mass and the infall time of their parent galaxy, we examine a subset of 15 simulations of galaxies and their star clusters from the E-MOSAICS project. E-MOSAICS is a suite of hydrodynamical simulations incorporating a sub-grid model for GC formation and evolution. We find that more massive accreted galaxies typically contribute younger and more metal rich GCs. This lower age results from a more extended cluster formation history in more massive galaxies. In addition, at fixed stellar mass, galaxies that are accreted later host younger clusters, because they can continue to form GCs without being subjected to environmental influences for longer. This explains the large range of ages observed for clusters associated with the Sagittarius dwarf galaxy in the halo of the Milky Way compared to clusters which are thought to have formed in satellites accreted early in the Milky Way's formation history. Using the ages of the GCs associated with the Sagittarius dwarf, we estimate a virial radius crossing lookback time (infall time) of $9.3 \pm 1.8 Gyr$.