Self-consistent proto-globular cluster formation in cosmological simulations of high-redshift galaxies
Self-consistent proto-globular cluster formation in cosmological simulations of high-redshift galaxies
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DOI：
10.1093/mnras/staa527
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发表时间：
2019-06
影响因子：
4.8
通讯作者：
Xiangcheng Ma;Michael Y. Grudić;E. Quataert;P. Hopkins;C. Faucher-Giguère;M. Boylan-Kolchin;A. Wetzel;Ji-hoon Kim;N. Murray;D. Keres̆
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作者：
Xiangcheng Ma;Michael Y. Grudić;E. Quataert;P. Hopkins;C. Faucher-Giguère;M. Boylan-Kolchin;A. Wetzel;Ji-hoon Kim;N. Murray;D. Keres̆
我们报道了来自真实环境反馈项目的z ≥ 5星系的高分辨率宇宙学放大模拟样本中束缚星星团的形成。我们发现束缚星系团优先形成于气体表面密度超过10 ^4\，\mathrm{ M}_{\odot }\，{\rm pc}^{-2}$的高压云中，在那里云尺度的星星形成效率接近1，并且在这些区域中诞生的年轻恒星在诞生时受到引力束缚。这些高压云被反馈驱动的风和/或高度富含气体的湍流环境中较小云/气流的碰撞压缩。新形成的团簇遵循幂律质量函数dN/dM <$M−2。星系团的形成效率在恒星质量为107- 10 ^{10}\，\mathrm{ M}_{\odot }$的星系中是相似的。星团恒星的年龄分布通常是几百万年，并随着星团质量的增加而增加。团簇成员的金属丰度分散度为10.08 dex，单位为$\rm [Z/H]$，并且不显著依赖于团簇质量。我们的发现支持了这样一种假设，即现今的古老球状星团（GC）是在高红移星系中相对正常的星星形成过程中形成的。用更严格/更宽松的星星形成模型进行模拟，形成了一个因子，即每形成一个恒星质量，就会有更多/更少的束缚星团，而质量函数的形状不变。在模拟中，较低的局部星星形成效率会在束缚星团中形成更多的恒星。由于有限的分辨率，模拟的集群比观察到的GC大。我们的模拟是第一个宇宙学模拟，在广泛的高红移星系中形成自洽的束缚星系团。
We report the formation of bound star clusters in a sample of high-resolution cosmological zoom-in simulations of z ≥ 5 galaxies from the Feedback In Realistic Environments project. We find that bound clusters preferentially form in high-pressure clouds with gas surface densities over $10^4\, \mathrm{ M}_{\odot }\, {\rm pc}^{-2}$, where the cloud-scale star formation efficiency is near unity and young stars born in these regions are gravitationally bound at birth. These high-pressure clouds are compressed by feedback-driven winds and/or collisions of smaller clouds/gas streams in highly gas-rich, turbulent environments. The newly formed clusters follow a power-law mass function of dN/dM ∼ M−2. The cluster formation efficiency is similar across galaxies with stellar masses of ∼107–$10^{10}\, \mathrm{ M}_{\odot }$ at z ≥ 5. The age spread of cluster stars is typically a few Myr and increases with cluster mass. The metallicity dispersion of cluster members is ∼0.08 dex in $\rm [Z/H]$ and does not depend on cluster mass significantly. Our findings support the scenario that present-day old globular clusters (GCs) were formed during relatively normal star formation in high-redshift galaxies. Simulations with a stricter/looser star formation model form a factor of a few more/fewer bound clusters per stellar mass formed, while the shape of the mass function is unchanged. Simulations with a lower local star formation efficiency form more stars in bound clusters. The simulated clusters are larger than observed GCs due to finite resolution. Our simulations are among the first cosmological simulations that form bound clusters self-consistently in a wide range of high-redshift galaxies.