Rapid growth of black holes accompanied with hot or warm outflows exposed to anisotropic super-Eddington radiation
Rapid growth of black holes accompanied with hot or warm outflows exposed to anisotropic super-Eddington radiation
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DOI：
10.1093/mnras/sty264
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发表时间：
2017-05
影响因子：
4.8
通讯作者：
Eishun Takeo;K. Inayoshi;K. Ohsuga;H. R. Takahashi;S. Mineshige
中科院分区：
文献类型：
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作者：
Eishun Takeo;K. Inayoshi;K. Ohsuga;H. R. Takahashi;S. Mineshige
为了研究早期宇宙中黑洞的快速增长，我们对质量为$10^3\leq M_{\rm BH}/M_{\odot} \lesssim 10^6$的黑洞（BH）进行了二维辐射流体动力学模拟。对于球对称流，只有当黑洞质量高于$\simeq 10^4~M_{\odot}(n_\infty/10^5~{\rm cm}^{-3})^{-1}(T_\infty/10^4~{\rm K})^{3/2}$（其中$n_\infty$和$T_\infty$是周围气体的密度和温度）时，从邦迪半径外到黑洞的超爱丁顿吸积才能不受辐射反馈的阻碍地发生。在这里，我们研究了来自一个亮度高于Eddington值（$L_{\rm Edd}$）的核吸积盘的各向异性辐射下的吸积流的性质，这是由于向双极方向的准直造成的。我们发现，与球对称的情况不同，即使是质量较小的黑洞$M_{\rm BH} < 10^4~M_{\odot}$也可以通过赤道面以$\gtrsim L_{\rm Edd}/c^2$的高吸积速率被周围的气体所吞噬，而电离区域则以$T\sim 10^5$ k的速度向极地方向扩张，产生热流出。对于质量较大的黑洞$M_{\rm BH}\gtrsim 5\times 10^5~M_{\odot}$，由于非径向气体运动，通过赤道面的中性气体完全覆盖了中心辐射区域。因此，各个方向的辐射都被阻挡了。由于氢气的有效重组，整个流动产生中性和温暖的气体$T \simeq 8000~{\rm K}$。中央黑洞以$\sim 5\times 10^4~L_{\rm Edd}/c^2$的平均速率通过赤道，这相当于从邦迪半径流入速率的$\sim 50~\%$。此外，中性氢吸收的辐射动量以黑洞进料速率$\sim 30~\%$和典型速度$\simeq 50~{\rm km~s}^{-1}$向双极方向产生温暖的流出。
We perform two-dimensional radiation hydrodynamical simulations of accretion flows onto a black hole (BH) with a mass of $10^3\leq M_{\rm BH}/M_{\odot} \lesssim 10^6$ in order to study rapid growth of BHs in the early Universe. For spherically symmetric flows, hyper-Eddington accretion onto the BH from outside the Bondi radius can occur unimpeded by radiation feedback only when the BH mass is higher than $\simeq 10^4~M_{\odot}(n_\infty/10^5~{\rm cm}^{-3})^{-1}(T_\infty/10^4~{\rm K})^{3/2}$, where $n_\infty$ and $T_\infty$ are the density and temperature of ambient gas. Here, we study the properties of accretion flows exposed to anisotropic radiation from a nuclear accretion disk with a luminosity higher than the Eddington value ($L_{\rm Edd}$) due to collimation toward the bipolar directions. We find that, unlike the spherically symmetric case, even less massive BHs with $M_{\rm BH} < 10^4~M_{\odot}$ can be fed by surrounding gas at high accretion rates of $\gtrsim L_{\rm Edd}/c^2$ through the equatorial plane, while ionized regions expand to the polar directions producing hot outflows with $T\sim 10^5$K. For more massive BHs with $M_{\rm BH}\gtrsim 5\times 10^5~M_{\odot}$, neutral gas through the equatorial plane totally covers the central radiating region due to the non-radial gas motions, and thus the emergent radiation in all directions is blocked. Because of efficient recombination by hydrogen, the entire flow results in neutral and warm gas with $T \simeq 8000~{\rm K}$ . The central BH is fed through the equator at the averaged rate of $\sim 5\times 10^4~L_{\rm Edd}/c^2$, which corresponds to $\sim 50~\%$ of the inflow rate from the Bondi radius. Moreover, radiation momentum absorbed by neutral hydrogen produces warm outflows toward the bipolar directions at $\sim 30~\%$ of the BH feeding rate and with a typical velocity of $\simeq 50~{\rm km~s}^{-1}$.