arXiv 2009.146732020-09-30astro-ph.GA

尘埃环核盘中中等质量黑洞的超爱丁顿质量增长

Super-Eddington mass growth of intermediate-mass black holes embedded in dusty circumnuclear disks

Daisuke Toyouchi, Kohei Inayoshi, Takashi Hosokawa, Rolf Kuiper

备注：: 23 pages, 10 figures, submitted to ApJ
DOI：: 10.3847/1538-4357/abcfc2

摘要：

我们进行了第一个三维辐射流体动力学模拟，调查嵌入在大规模的自引力，尘埃核吸积盘的中间质量黑洞（IMBHs）的增长。我们探讨了质量吸积效率对气体金属丰度$Z$和质量注入的依赖性，从外星系盘$\dot{M}_{\rm in}$在超爱丁顿吸积率，并发现中央BH可以美联储在超过爱丁顿率只有当尘埃盘变得足够的光学厚度电离辐射。在这种情况下，由于光蒸发而从盘的质量流出被抑制，因此质量注入速率的大部分（$\gtrsim 40\%$）可以供给中心BH。条件表示为$\dot{M}_{\rm in} > 2.2\times 10^{-1}~M_\odot ~{\rm yr}^{-1} (1+Z/10^{-2}~Z_\odot)^{-1}(c_{\rm s}/10~{\rm km~s}^{-1})$，其中$c_{\rm s}$是气体盘中的声速。随着数值分辨率的增加，剧烈的盘碎裂降低了盘的表面密度，而通过形成团块的动力学加热使盘的厚度更高。其结果是，光蒸发质量损失率上升，从而增加了临界注入速率固定金属丰度。这个过程使超爱丁顿生长的BH，直到BH质量达到$M_{\rm BH} \sim 10^{7-8}~M_\odot$，这取决于主机的暗物质晕和金属富集的历史属性。在原星系的集合体中，在$z\sim 15-20$质量变化为3-4 $σ$的过密区域中形成的种子黑洞能够经历短时间的快速生长，然后过渡到爱丁顿限制生长阶段，成为在$z>6-7$观测到的超大质量黑洞。

英文摘要：

We perform the first three-dimensional radiation hydrodynamical simulations that investigate the growth of intermediate-mass BHs (IMBHs) embedded in massive self-gravitating, dusty nuclear accretion disks. We explore the dependence of mass accretion efficiency on the gas metallicity $Z$ and mass injection at super-Eddington accretion rates from the outer galactic disk $\dot{M}_{\rm in}$, and find that the central BH can be fed at rates exceeding the Eddington rate only when the dusty disk becomes sufficiently optically thick to ionizing radiation. In this case, mass outflows from the disk owing to photoevaporation is suppressed and thus a large fraction ($\gtrsim 40\%$) of the mass injection rate can feed the central BH. The conditions are expressed as $\dot{M}_{\rm in} > 2.2\times 10^{-1}~M_\odot ~{\rm yr}^{-1} (1+Z/10^{-2}~Z_\odot)^{-1}(c_{\rm s}/10~{\rm km~s}^{-1})$, where $c_{\rm s}$ is the sound speed in the gaseous disk. With increasing numerical resolution, vigorous disk fragmentation reduces the disk surface density and dynamical heating by formed clumps makes the disk thickness higher. As a result, the photoevaorative mass-loss rate rises and thus the critical injection rate increases for fixed metallicity. This process enables super-Eddington growth of BHs until the BH mass reaches $M_{\rm BH} \sim 10^{7-8}~M_\odot$, depending on the properties of the host dark-matter halo and metal-enrichment history. In the assembly of protogalaxies, seed BHs that form in overdense regions with a mass variance of 3-4$σ$ at $z\sim 15-20$ are able to undergo short periods of their rapid growth and transits into the Eddington-limited growth phase afterwards to be supermassive BHs observed at $z>6-7$.

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