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arXiv 0903.4492astro-ph.CO
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分级宇宙中的超大质量黑洞:一般框架和观测检验

Supermassive Black Holes in the Hierarchical Universe: A General Framework and Observational Tests

Yue Shen

摘要:

我们提出了一个简单的框架,超大质量黑洞(SMBHs)的生长和演化的分级结构形成范式。在我们的模型中,黑洞吸积是在宿主暗物质晕之间的主要合并(质量比>~0.3)过程中触发的。类星体光度的连续演化遵循一个普遍的光变曲线形式:初始的指数增长,以恒定的爱丁顿比为单位,直到它达到峰值光度,其次是幂律衰减。假设峰值光度与合并后的晕质量相关,我们将光变曲线与类星体活动的触发率卷积,预测类星体的光度函数(LF)。我们的模型再现了在0.5 <z <4.5处观察到的LF,用于当前光学和X射线调查探测的全部光度范围。我们的模型再现了观测到的红移演化和光度依赖的线性偏置类星体/活动星系核集群。由于瞬时光度和晕质量之间的散射,类星体/活动星系核成团在低到中等光度时对光度的依赖很弱,但在高光度端和高红移时,线性偏差随光度迅速上升。在我们的模型中,爱丁顿比分布大致呈对数正态分布,从高光度类星体(L_bol>~10^46 erg s ^-1)到低光度活动星系核(L_bol <~10^45 erg s ^-1),这种分布会变宽并向较低的平均值移动,与观测结果吻合得很好。

英文摘要:

(Abridged) We present a simple framework for the growth and evolution of supermassive black holes (SMBHs) in the hierarchical structure formation paradigm. In our model, black hole accretion is triggered during major mergers (mass ratio>~0.3) between host dark matter halos. The successive evolution of quasar luminosities follows a universal light curve form: an initial exponential growth at constant Eddington ratio of order unity until it reaches the peak luminosity, followed by a power-law decay. Assuming that the peak luminosity correlates with the post-merger halo mass, we convolve the light curve with the triggering rate of quasar activity to predict the quasar luminosity function (LF). Our model reproduces the observed LF at 0.5<z<4.5 for the full luminosity ranges probed by current optical and X-ray surveys. Our model reproduces both the observed redshift evolution and luminosity dependence of the linear bias of quasar/AGN clustering. Due to the scatter between instantaneous luminosity and halo mass, quasar/AGN clustering weakly depends on luminosity at low to intermediate luminosities; but the linear bias rises rapidly with luminosity at the high luminosity end and at high redshift. In our model, the Eddington ratio distribution is roughly log-normal, which broadens and shifts to lower mean values from high luminosity quasars (L_bol>~10^46 erg s^-1) to low luminosity AGNs (L_bol<~ 10^45 erg s^-1), in good agreement with observations.

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