Radiation hydrodynamics simulations of the formation of direct-collapse supermassive stellar systems
Radiation hydrodynamics simulations of the formation of direct-collapse supermassive stellar systems
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DOI：
10.1093/mnras/sty086
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发表时间：
2017-11
影响因子：
4.8
通讯作者：
Sunmyon Chon;T. Hosokawa;N. Yoshida
中科院分区：
文献类型：
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作者：
Sunmyon Chon;T. Hosokawa;N. Yoshida
质量约为 10^4 Msun 的超大质量恒星 (SMS) 的形成是在早期宇宙中形成超大质量黑洞的一条有希望的途径。所谓的直接塌缩（DC）模型假设这样的 SMS 是在附近恒星形成星系辐射的热气体云中形成的。我们使用三维辐射流体动力学模拟在完全宇宙学背景下研究 DC SMS 的形成。我们使用 Chon 等人的宇宙学模拟的输出来初始化我们的模拟。 （2016），其中识别出两个 DC 气体云。从胚胎原恒星的形成到它们的生长，经历了十万年的长期演化。我们表明，附近星系潮汐力的强度决定了形成恒星的多样性并影响原恒星的生长。在一种情况下，当强大的潮汐力显着拉伸坍缩的云时，通过细丝破碎形成多个星盘系统。每个星周盘都会发生小规模的碎裂，最终形成10多颗质量为数倍10^3Msun的恒星。有趣的是，其中大约一半被发现是大质量双星。另一种情况是，气体云在相对较弱的潮汐场下塌缩成近球形，形成单一星盘系统。经过十万年的演化，仅发现了少数质量约为 10^4 Msun 的 SMS，并且预计这些 SMS 将通过气体吸积进一步增长，并在其生命结束时留下巨大的黑洞。
Formation of supermassive stars (SMSs) with mass ~10^4 Msun is a promising pathway to seed the formation of supermassive black holes in the early universe. The so-called direct-collapse (DC) model postulates that such an SMS forms in a hot gas cloud irradiated by a nearby star-forming galaxy. We study the DC SMS formation in a fully cosmological context using three-dimensional radiation hydrodynamics simulations. We initialize our simulations using the outputs of the cosmological simulation of Chon et al. (2016), where two DC gas clouds are identified. The long-term evolution over a hundred thousand years is followed from the formation of embryo protostars through their growth to SMSs. We show that the strength of the tidal force by a nearby galaxy determines the multiplicity of the formed stars and affects the protostellar growth. In one case, where a collapsing cloud is significantly stretched by strong tidal force, multiple star-disk systems are formed via filament fragmentation. Small-scale fragmentation occurs in each circumstellar disk, and more than 10 stars with masses of a few times 10^3 Msun are finally formed. Interestingly, about a half of them are found as massive binary stars. In the other case, the gas cloud collapses nearly spherically under a relatively weak tidal field, and a single star-disk system is formed. Only a few SMSs with masses ~ 10^4 Msun are found already after evolution of a hundred thousand years, and the SMSs are expected to grow further by gas accretion and to leave massive blackholes at the end of their lives.