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arXiv 2209.01427astro-ph.HE
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超爱丁顿流的大尺度外流结构和辐射性质:对吸积率的依赖

Large-scale outflow structure and radiation properties of super-Eddington flow: Dependence on the accretion rates

Shogo Yoshioka, Shin Mineshige, Ken Ohsuga, Tomohisa Kawashima, Takaaki Kitaki

摘要:

为了精确地评估超爱丁顿吸积体对环境的影响,必须确保足够大的模拟箱和较长的计算时间,以尽可能避免数值设置中的任何伪影。本文在大型模拟箱中对$10~M_\odot$黑洞进行了轴对称二维辐射流体动力学模拟,研究了不同吸积率${\dot M}_{\rm BH} = (110 - 380) ~L_{\rm Edd}/c^2$下超爱丁顿吸积流的大尺度外流结构和辐射性质.当离心力与引力平衡时,流入物质的开普勒半径固定为2430史瓦西半径,随着${\dot M}_{\rm BH}$的增加,机械光度的增长比辐射光度的增长快。特别是当从接近正面的方向看时,各向同性机械发光度与${\dot M}_{\rm BH}^{2.7}$成比例地增长,而总机械发光度与${\dot M}_{\rm BH}^{1.7}$成比例。前者的原因是,${\dot M}_{\rm BH}$越高,盘表面就变得越垂直膨胀,这使得辐射场更局限于围绕旋转轴的区域中,从而强烈地加速流出的气体。根据流出气体能否到达模拟箱的外边界,将流出气体分为纯流出气体和失败流出气体。失败流出的分数随着${\dot M}_{\rm BH}$的减小而减小。我们分析了沿每个流出轨迹的物理量,发现伯努利参数($Be$)不是区分纯流出和失败流出的好指标,因为它从来不是恒定的,因为辐射压力的持续加速。纯流出可以出现,即使$Be < 0$在发射点。

英文摘要:

In order to precisely evaluate the impacts by super-Eddington accretors to their environments, it is essential to assure a large enough simulation box and long computational time to avoid any artefacts from numerical settings as much as possible. In this paper, we carry out axisymmetric two-dimensional radiation hydrodynamic simulations around a $10~M_\odot$ black hole in large simulation boxes and study the large-scale outflow structure and radiation properties of super-Eddington accretion flow for a variety of black hole accretion rates, ${\dot M}_{\rm BH} = (110 - 380) ~L_{\rm Edd}/c^2$. The Keplerian radius of the inflow material, at which centrifugal force balances with gravitational force, is fixed to 2430 Schwarzschild radii.We find that the mechanical luminosity grows more rapidly than the radiation luminosity with an increase of ${\dot M}_{\rm BH}$. When seen from a nearly face-on direction, especially, the isotropic mechanical luminosity grows in proportion to ${\dot M}_{\rm BH}^{2.7}$, while the total mechanical luminosity is proportional to ${\dot M}_{\rm BH}^{1.7}$. The reason for the former is that the higher ${\dot M}_{\rm BH}$ is, the more vertically inflated becomes the disk surface, which makes radiation fields more confined in the region around the rotation axis, thereby strongly accelerating outflowing gas. The outflow is classified into pure outflow and failed outflow, depending whether outflowing gas can reach the outer boundary of the simulation box or not. The fraction of the failed outflow decreases with a decrease of ${\dot M}_{\rm BH}$. We analyze physical quantities along each outflow trajectory, finding that the Bernoulli parameter ($Be$) is not a good indicator to discriminate pure and failed outflows, since it is never constant because of continuous acceleration by radiation-pressure force.Pure outflow can arise, even if $Be < 0$ at the launching point.

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