标题： 初始密度分布对巨分子云中大质量星团形成的影响 显示英文标题

标题： Effects of initial density profiles on massive star cluster formation in giant molecular clouds

摘要： 我们进行了一系列流体动力学模拟，以研究巨大分子云（GMCs）的初始密度分布如何影响其后续演化。 我们发现整个云的恒星形成持续时间和总恒星形成效率对不同分布的选择不敏感，而是主要由引力坍缩和恒星反馈之间的相互作用控制。 尽管有这种相似性，具有不同分布的GMC表现出截然不同的恒星形成模式。 对于较浅的分布，GMC首先分裂成许多自引力核心，并形成分布在整个云中的子聚类。 这些子聚类随后以“分层”的方式组装成中心聚类。 相反，对于更陡峭的分布，在云的中心迅速形成一个大质量聚类，然后通过气体吸积逐渐增加其质量。 因此，从较浅分布的云中出现的中心聚类质量较小，并且旋转较少，与较陡分布的聚类相比。 这是因为1）在较浅分布中，大量质量和角动量存储在无法合并到中心聚类的子聚类的轨道运动中；2）在较浅分布中频繁的分层合并导致通过剧烈松弛和潮汐破坏进一步损失质量和角动量。 令人鼓舞的是，较陡分布中的聚类旋转程度与最近对年轻和中等年龄聚类的观测结果一致。 我们推测，旋转的球状星团很可能是在宇宙早期通过“吸积”模式，从中心集中云中形成的。 显示英文摘要

摘要： We perform a suite of hydrodynamic simulations to investigate how initial density profiles of giant molecular clouds (GMCs) affect their subsequent evolution. We find that the star formation duration and integrated star formation efficiency of the whole clouds are not sensitive to the choice of different profiles but are mainly controlled by the interplay between gravitational collapse and stellar feedback. Despite this similarity, GMCs with different profiles show dramatically different modes of star formation. For shallower profiles, GMCs first fragment into many self-gravitation cores and form sub-clusters that distributed throughout the entire clouds. These sub-clusters are later assembled ``hierarchically'' to central clusters. In contrast, for steeper profiles, a massive cluster is quickly formed at the center of the cloud and then gradually grows its mass via gas accretion. Consequently, central clusters that emerged from clouds with shallower profiles are less massive and show less rotation than those with the steeper profiles. This is because 1) a significant fraction of mass and angular momentum in shallower profiles is stored in the orbital motion of the sub-clusters that are not able to merge into the central clusters 2) frequent hierarchical mergers in the shallower profiles lead to further losses of mass and angular momentum via violent relaxation and tidal disruption. Encouragingly, the degree of cluster rotations in steeper profiles is consistent with recent observations of young and intermediate-age clusters. We speculate that rotating globular clusters are likely formed via an ``accretion'' mode from centrally-concentrated clouds in the early Universe.