Cluster assembly and the origin of mass segregation in the STARFORGE simulations
Cluster assembly and the origin of mass segregation in the STARFORGE simulations
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STARFORGE 模拟中的团簇组装和质量偏析的起源
DOI：
10.1093/mnras/stac1737
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发表时间：
2022
影响因子：
4.8
通讯作者：
Hopkins, Philip F.
中科院分区：
文献类型：
--
作者：
Guszejnov, Dávid;Markey, Carleen;Offner, Stella S. R.;Grudić, Michael Y.;Faucher-Giguère, Claude-André;Rosen, Anna L.;Hopkins, Philip F.
恒星在密集的星团环境中形成，新形成的恒星的反馈最终会喷出气体，终止恒星的形成，留下一个或多个星团。使用STARFORGE模拟，可以在分子云中完整地模拟这一过程，同时显式地演变气体辐射和磁场，并跟随个别低质量恒星的形成。我们发现，单个恒星形成点合并形成更大的结构，同时仍在吸积气体。因此，集群是通过一系列合并来组装的。在星团组装过程中，有一小部分恒星被抛出星团；我们发现抛射出的恒星群的质量分布与星团内恒星的质量分布没有显著差异。恒星形成地是星系团的积木，一开始是质量分离的，中心有一颗或几颗大质量恒星。当它们合并时，新形成的星系团保持了这一特征，导致它们具有质量分离的子结构，而不是自身集中凝聚。合并的星系团通过成员之间的动态相互作用松弛到中心凝聚的质量分离构型，但在反馈将剩余气体从星系团中排出之前，这一过程并未完成。在模拟运行中，没有气体的星团随后变得松散和分裂。我们发现，湍流驱动和周期性的云几何形状可以显著减少聚集和防止气体排放。同时，尽管恒星形成历史明显不同，但初始表面密度和湍流水平对星团演化几乎没有定性影响。
Stars form in dense, clustered environments, where feedback from newly formed stars eventually ejects the gas, terminating star formation and leaving behind one or more star clusters. Using the STARFORGE simulations, it is possible to simulate this process in its entirety within a molecular cloud, while explicitly evolving the gas radiation and magnetic fields and following the formation of individual, low-mass stars. We find that individual star-formation sites merge to form ever larger structures, while still accreting gas. Thus clusters are assembled through a series of mergers. During the cluster assembly process, a small fraction of stars are ejected from their clusters; we find no significant difference between the mass distribution of the ejected stellar population and that of stars inside clusters. The star-formation sites that are the building blocks of clusters start out mass segregated with one or a few massive stars at their centre. As they merge the newly formed clusters maintain this feature, causing them to have mass-segregated substructures without themselves being centrally condensed. The merged clusters relax to a centrally condensed mass-segregated configuration through dynamical interactions between their members, but this process does not finish before feedback expels the remaining gas from the cluster. In the simulated runs, the gas-free clusters then become unbound and breakup. We find that turbulent driving and a periodic cloud geometry can significantly reduce clustering and prevent gas expulsion. Meanwhile, the initial surface density and level of turbulence have little qualitative effect on cluster evolution, despite the significantly different star formation histories.