COSMOLOGICAL SIMULATIONS OF EARLY BLACK HOLE FORMATION: HALO MERGERS, TIDAL DISRUPTION, AND THE CONDITIONS FOR DIRECT COLLAPSE
COSMOLOGICAL SIMULATIONS OF EARLY BLACK HOLE FORMATION: HALO MERGERS, TIDAL DISRUPTION, AND THE CONDITIONS FOR DIRECT COLLAPSE
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DOI：
10.3847/0004-637x/832/2/134
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发表时间：
2016-03
期刊：
影响因子：
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通讯作者：
Sunmyon Chon;S. Hirano;T. Hosokawa;N. Yoshida
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作者：
Sunmyon Chon;S. Hirano;T. Hosokawa;N. Yoshida
巨大的原始气体云的引力塌缩被认为是早期宇宙中超大质量黑洞形成的一条有希望的路径。我们在完全宇宙学的背景下研究所谓的直接塌缩（DC）黑洞形成的条件。我们将早期星系形成的半解析模型与由暗物质 N 体模拟构建的晕合并树相结合。我们在一侧的体积中总共定位了 68 个可能的 DC 站点。然后，我们对 42 个选定的光晕进行流体动力学模拟，以详细研究其中的大量云的演化。我们只发现两个成功的案例，其中气体云迅速坍塌形成恒星。在其他情况下，附近的巨大光环施加的潮汐力可以防止引力塌缩，否则它应该充当直流电所需的辐射源。冲压压力剥离扰乱了接近源头的云。在许多情况下，直流光晕和附近的光源光晕会在云塌陷之前合并。当直流晕通过大合并聚集时，气体密度迅速增加，引发引力不稳定。根据我们的宇宙学模拟，我们得出结论，直流的事件发生率比之前研究报告的要小一个数量级，尽管绝对发生率仍然受到很差的限制。有必要跟踪直流云及其附近晕的动态演化，以确定直流的临界辐射通量。
Gravitational collapse of a massive primordial gas cloud is thought to be a promising path for the formation of supermassive black holes in the early universe. We study conditions for the so-called direct collapse (DC) black hole formation in a fully cosmological context. We combine a semianalytic model of early galaxy formation with halo merger trees constructed from dark matter N-body simulations. We locate a total of 68 possible DC sites in a volume of on a side. We then perform hydrodynamics simulations for 42 selected halos to study in detail the evolution of the massive clouds within them. We find only two successful cases where the gas clouds rapidly collapse to form stars. In the other cases, gravitational collapse is prevented by the tidal force exerted by a nearby massive halo, which otherwise should serve as a radiation source necessary for DC. Ram pressure stripping disturbs the cloud approaching the source. In many cases, a DC halo and its nearby light source halo merge before the onset of cloud collapse. When the DC halo is assembled through major mergers, the gas density increases rapidly to trigger gravitational instability. Based on our cosmological simulations, we conclude that the event rate of DC is an order of magnitude smaller than reported in previous studies, although the absolute rate is still poorly constrained. It is necessary to follow the dynamical evolution of a DC cloud and its nearby halo(s) in order to determine the critical radiation flux for DC.