具有非高斯原始密度扰动的黑洞的形成和增长
Black hole formation and growth with non-Gaussian primordial density perturbations
摘要：
由质量估计超过10亿太阳质量的大质量黑洞（BH）提供动力的类星体已经在红移6或更高的位置被发现。这样的黑洞的存在需要在爱丁顿极限下几乎连续的生长，在它们的整个生命周期中，大约10亿年。在本文中，我们探讨的可能性，正偏斜的尺度依赖的非高斯原始波动可能会减轻组装的大规模黑洞。特别是，它们在高红移时产生更多的低质量晕，从而改变了金属和紫外线通量的产生，这些被认为是BH形成的重要因素。此外，更高数量的祖先和几乎相等质量的晕合并将促进BH-BH合并和合并驱动的吸积提供的质量增加。我们使用一组两个宇宙学模拟，无论是高斯或尺度依赖的非高斯原始波动进行概念验证实验，以估计BH的形成和增长是如何改变的。我们估计BH数密度和BH形成的晕的分数，两个模拟和BH形成的两个流行的场景（残留的第一代恒星和直接崩溃的金属和分子氢的情况下）。我们发现，黑洞形成的晕的分数几乎是相同的，但非高斯原始扰动增加了黑洞的总数密度为两个黑洞形成的情况。我们还发展BH合并树提取的模拟和发现，非高斯性增加BH的质量和最大的BH的数量。
英文摘要：
Quasars powered by massive black holes (BHs) with mass estimates above a billion solar masses have been identified at redshift 6 and beyond. The existence of such BHs requires almost continuous growth at the Eddington limit for their whole lifetime, of order of one billion years. In this paper, we explore the possibility that positively skewed scale-dependent non-Gaussian primordial fluctuations may ease the assembly of massive BHs. In particular, they produce more low-mass halos at high redshift, thus altering the production of metals and ultra-violet flux, believed to be important factors in BH formation. Additionally, a higher number of progenitors and of nearly equal-mass halo mergers would boost the mass increase provided by BH-BH mergers and merger-driven accretion. We use a set of two cosmological simulations, with either Gaussian or scale-dependent non-Gaussian primordial fluctuations to perform a proof-of-concept experiment to estimate how BH formation and growth are altered. We estimate the BH number density and the fraction of halos where BHs form, for both simulations and for two popular scenarios of BH formation (remnants of the first generation of stars and direct collapse in the absence of metals and molecular hydrogen). We find that the fractions of halos where BHs form are almost identical, but that non-Gaussian primordial perturbations increase the total number density of BHs for the both BH formation scenarios. We also evolve BHs using merger trees extracted from the simulations and find that non-Gaussianities increase both the BH masses and the number of the most massive BHs.
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