arXiv 1104.47972011-04-25astro-ph.CO

早期宇宙中大质量黑洞种子的形成和演化

The formation and evolution of massive black hole seeds in the early Universe

Priyamvada Natarajan

备注：: 18 pages, invited review, to appear in the Chandra Centennial issue of the Bulletin of the Astronomical Society of India

摘要：

跟踪高红移种子黑洞质量的演化到晚期，我们研究了今天可观察到的签名。这些巨大的初始黑洞种子形成于极高的红移，来自于前星系气体盘的直接坍缩。填充暗物质晕与种子形成这种方式，我们按照质量大会的历史，这些黑洞到目前为止，使用蒙特卡洛合并树的方法。利用这种形式主义，我们预测的黑洞的质量函数在高红移和目前的时间;在宇宙中的黑洞的综合质量密度;吸积黑洞的光度函数作为红移和散射的函数，在观察到的，当地的M-西格玛关系。比较“轻”种子模型的预测与这些大规模的种子，我们发现，显着的差异主要出现在低质量端的现今黑洞质量函数。然而，我们所有的模型都预测，低表面亮度，膨胀少的星系与大光盘是最不可能的网站形成的大规模种子黑洞在高红移。在高红移时，种子形成的效率直接影响z=0时星系中黑洞的占有率。这种效应在低质量星系中更为明显。这是这里研究的模型和人口III残留“轻”种子模型之间的关键区别。我们发现，存在着人口的低质量星系，不主机核黑洞。我们的预测的形状的M-西格玛关系在低质量端和增加散射最近得到证实的观测。

英文摘要：

Tracking the evolution of high redshift seed black hole masses to late times, we examine the observable signatures today. These massive initial black hole seeds form at extremely high redshifts from the direct collapse of pre-galactic gas discs. Populating dark matter halos with seeds formed in this fashion, we follow the mass assembly history of these black holes to the present time using a Monte-Carlo merger tree approach. Utilizing this formalism, we predict the black hole mass function at high redshifts and at the present time; the integrated mass density of black holes in the Universe; the luminosity function of accreting black holes as a function of redshift and the scatter in observed, local M-sigma relation. Comparing the predictions of the `light' seed model with these massive seeds we find that significant differences appear predominantly at the low mass end of the present day black hole mass function. However, all our models predict that low surface brightness, bulge-less galaxies with large discs are least likely to be sites for the formation of massive seed black holes at high redshifts. The efficiency of seed formation at high redshifts has a direct influence on the black hole occupation fraction in galaxies at z=0. This effect is more pronounced for low mass galaxies. This is the key discriminant between the models studied here and the Population III remnant `light' seed model. We find that there exists a population of low mass galaxies that do not host nuclear black holes. Our prediction of the shape of the M-sigma relation at the low mass end and increased scatter has recently been corroborated by observations.

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