Transition of the initial mass function in the metal-poor environments
Transition of the initial mass function in the metal-poor environments
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贫金属环境中初始质量函数的转变
DOI：
10.1093/mnras/stab2497
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发表时间：
2021
影响因子：
4.8
通讯作者：
Schneider Raffaella
中科院分区：
文献类型：
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作者：
Chon Sunmyon;Omukai Kazuyuki;Schneider Raffaella
我们使用三维流体动力学模拟研究低金属丰度环境中星团的形成。从湍流云核心开始，我们跟踪具有不同金属丰度（从 10−6 到 0.1 Z⊙）的原恒星系统的形成和生长。尘埃颗粒引起的冷却促进了小尺度的碎裂和 M*∼ 0.01–0.1 M⊙ 低质量恒星的形成。虽然低质量恒星的数量随着金属丰度的增加而增加，但当Z/Z⊙≳ 10−5时，与Chabrier初始质量函数（IMF）相比，Z/Z⊙≲ 10−2时的恒星质量分布仍然是头重脚轻。在这些情况下，恒星形成是在湍流运动衰减之后开始的，并且单个大质量云核整体塌缩形成中央大质量恒星系统。星周盘优先将质量供给中心大质量恒星，使得质量分布呈头重脚轻的状态。当Z/Z⊙= 0.1时，湍流的碰撞促进了星形形成的开始，并且由于有效的精细结构线冷却而形成高度丝状结构。在这种情况下，大质量恒星的质量供应受到当地气藏的限制，并且质量在恒星之间共享，从而形成类似夏布里埃的IMF。我们得出的结论是，湍流运动尺度的冷却促进了丝状结构的发展，并且是导致当今 IMF 的重要因素。
We study star cluster formation in a low-metallicity environment using three-dimensional hydrodynamic simulations. Starting from a turbulent cloud core, we follow the formation and growth of protostellar systems with different metallicities ranging from 10−6to 0.1 Z⊙. The cooling induced by dust grains promotes fragmentation at small scales and the formation of low-mass stars withM*∼ 0.01–0.1 M⊙. While the number of low-mass stars increases with metallicity, whenZ/Z⊙≳ 10−5, the stellar mass distribution is still top-heavy forZ/Z⊙≲ 10−2compared to the Chabrier initial mass function (IMF). In these cases, star formation begins after the turbulent motion decays and a single massive cloud core monolithically collapses to form a central massive stellar system. The circumstellar disc preferentially feeds the mass to the central massive stars, making the mass distribution top-heavy. WhenZ/Z⊙= 0.1, collisions of the turbulent flows promote the onset of the star formation and a highly filamentary structure develops owing to efficient fine-structure line cooling. In this case, the mass supply to the massive stars is limited by the local gas reservoir and the mass is shared among the stars, leading to a Chabrier-like IMF. We conclude that cooling at the scales of the turbulent motion promotes the development of the filamentary structure and works as an important factor leading to the present-day IMF.