Rapid Black Hole Growth under Anisotropic Radiation Feedback
Rapid Black Hole Growth under Anisotropic Radiation Feedback
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DOI：
10.1093/mnras/stx769
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发表时间：
2016-10
影响因子：
4.8
通讯作者：
K. Sugimura;T. Hosokawa;H. Yajima;K. Omukai
中科院分区：
文献类型：
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作者：
K. Sugimura;T. Hosokawa;H. Yajima;K. Omukai
高红移（z > 6）超大质量黑洞（BH）的发现可能表明快速（或超爱丁顿）气体吸积有助于它们的快速增长。在这里，我们研究了这种快速吸积的原始气体的中等质量（10^2 - 10^5 M_sun）BH下各向异性辐射反馈。我们进行二维辐射流体动力学模拟，解决整个邦迪半径的流动结构，从远处的邦迪半径下降到一个中心部分，这是大于一个环BH吸积盘。在考虑自遮蔽效应的情况下，建立了解析模型。我们表明，流进入稳定状态，其中的流动结构由两个不同的部分组成：（1）双极电离流出区域，在那里的气体被热气体压力和超爱丁顿辐射压力向外推，和（2）赤道中性流入区域，在那里的气体福尔斯下降到中央BH不受辐射反馈的影响。由此产生的吸积率是远远高于在各向同性辐射的情况下，远远超过爱丁顿限制的速度达到一个值略低于邦迪之一。赤道流入区的张角由中心辐射的光度和方向依赖性决定。我们发现，光蒸发从其表面设置的临界开角约为10度以下的吸积到BH淬火。我们认为，阴影效应甚至允许恒星残骸黑洞迅速成长到足以成为高红移超大质量黑洞。
Discovery of high-redshift (z > 6) supermassive black holes (BHs) may indicate that the rapid (or super-Eddington) gas accretion has aided their quick growth. Here, we study such rapid accretion of the primordial gas on to intermediate-mass (10^2 - 10^5 M_sun) BHs under anisotropic radiation feedback. We perform two-dimensional radiation hydrodynamics simulations that solve the flow structure across the Bondi radius, from far outside of the Bondi radius down to a central part which is larger than a circum-BH accretion disc. The radiation from the unresolved circum-BH disc is analytically modeled considering self-shadowing effect. We show that the flow settles into a steady state, where the flow structure consists of two distinct parts: (1) bipolar ionized outflowing regions, where the gas is pushed outward by thermal gas pressure and super-Eddington radiation pressure, and (2) an equatorial neutral inflowing region, where the gas falls toward the central BH without affected by radiation feedback. The resulting accretion rate is much higher than that in the case of isotropic radiation, far exceeding the Eddington-limited rate to reach a value slightly lower than the Bondi one. The opening angle of the equatorial inflowing region is determined by the luminosity and directional dependence of the central radiation. We find that photoevaporation from its surfaces set the critical opening angle of about ten degrees below which the accretion to the BH is quenched. We suggest that the shadowing effect allows even stellar-remnant BHs to grow rapidly enough to become high-redshift supermassive BHs.