arXiv 1901.045142019-01astro-ph.HEastro-ph.GA

早期宇宙中黑洞的超爱丁顿生长：盘辐射谱的影响

Super-Eddington growth of black holes in the early Universe: effects of disk radiation spectra

Eishun Takeo, Kohei Inayoshi, Ken Ohsuga, Hiroyuki R. Takahashi, Shin Mineshige

备注：: 13 pages, 9 figures, 2 tables, accepted by MNRAS
DOI：: 10.1093/mnras/stz1899

摘要：

为了研究早期宇宙中黑洞的快速增长，我们研究了质量为$M_{\rm BH}$的黑洞（BH）在密度为$n_{\infty}$的初始均匀气体云中吸积流的性质.在以前的工作中，从外部的邦迪半径的超爱丁顿吸积的条件进行了研究，假设在中心BH附近产生的辐射有一个单一的幂律谱$ν^{-α}$在$hν\geq 13.6~{\rm eV}$（$α\sim 1.5$）。然而，辐射光谱依赖于BH质量和吸积率。在这里，我们进行二维多频辐射流体动力学模拟考虑到更现实的辐射光谱与核吸积盘的属性。我们发现，过渡到超爱丁顿吸积的条件是减轻了广泛的质量（$10\lesssim M_{\rm BH}/M_{\odot} \lesssim 10^6$），因为吸积盘光谱的光电离效率低于那些单次幂律谱。对于圆盘光谱，由于辐射光谱变得太硬而不能吸收气体，因此在较低的BH质量下更有可能发生超爱丁顿跃迁。即使当吸积流暴露于各向异性辐射，由于辐射光谱的影响收缩的电离区域，并可能导致过渡到一个完全中性的吸积阶段。最后，通过推广我们的模拟结果，我们构建了一个新的分析标准所需的超爱丁顿吸积; $(M_{\rm BH}/10^5~M_{\odot}) (n_{\infty}/10^4~{\rm cm^{-3}}) \gtrsim 2.4~ (\langleε\rangle /100~{\rm eV})^{-5/9}$，其中$\langleε\rangle$是电离辐射的中心BH的平均能量。

英文摘要：

We investigate the properties of accretion flows onto a black hole (BH) with a mass of $M_{\rm BH}$ embedded in an initially uniform gas cloud with a density of $n_{\infty}$ in order to study rapid growth of BHs in the early Universe. In previous work, the conditions for super-Eddington accretion from outside the Bondi radius were studied by assuming that radiation produced at the vicinity of the central BH has a single-power-law spectrum $ν^{-α}$ at $hν\geq 13.6~{\rm eV}$ ($α\sim 1.5$). However, radiation spectra depends on the BH mass and accretion rate. Here, we perform two-dimensional multi-frequency radiation hydrodynamical simulations taking into account more realistic radiation spectra associated with the properties of nuclear accretion disks. We find that the condition for a transition to super-Eddington accretion is alleviated for a wide range of masses ($10\lesssim M_{\rm BH}/M_{\odot} \lesssim 10^6$) because photoionization for accretion disk spectra are less efficient than those for single-power-law spectra. For disk spectra, the transition to super-Eddington is more likely to occur for lower BH masses because the radiation spectra become too hard to ionize the gas. Even when accretion flows are exposed to anisotropic radiation, the effect due to radiation spectra shrinks the ionized region and likely leads to the transition to a wholly neutral accretion phase. Finally, by generalizing our simulation results, we construct a new analytical criterion required for super-Eddington accretion; $(M_{\rm BH}/10^5~M_{\odot}) (n_{\infty}/10^4~{\rm cm^{-3}}) \gtrsim 2.4~ (\langleε\rangle /100~{\rm eV})^{-5/9}$, where $\langleε\rangle$ is the mean energy of ionizing radiation from the central BH.

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