The role of feedback in accretion on low-luminosity AGN: Sgr A* case study
The role of feedback in accretion on low-luminosity AGN: Sgr A* case study
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DOI：
10.1093/mnras/stv584
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发表时间：
2015-03
影响因子：
4.8
通讯作者：
J. Cuadra;S. Nayakshin;Q. Wang
中科院分区：
文献类型：
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作者：
J. Cuadra;S. Nayakshin;Q. Wang
我们提出的数值模型的气体动力学的内秒差距的银河系中心。我们从它的起源跟踪气体作为几个观测到的年轻大质量恒星的恒星风，直到它被中心黑洞捕获或离开系统。与我们以前的模型不同，我们包括从内部吸积流流出。两种不同类型的流出建模：（i）瞬时响应反馈模式，其中流出率与当前黑洞气体捕获率成正比;和（ii）爆发模式，这是更强，但持续有限的时间。后一种情况可能与人马座A* 特别相关，因为有证据表明人马座A* 在最近的过去要亮得多。我们发现，这两种类型的外流扰动附近的邦迪半径和黑洞捕获率显着的气体动力学。这种影响比资金外流本身持续的时间更长。我们还比较了球对称和准直外流的影响，发现后者在将其能量传递到捕获半径附近的周围气体时效率要低得多。我们的研究结果表明，吸积反馈是重要的非辐射吸积流不仅在内部，而且在捕获半径之外。不考虑反馈流出的稳态邦迪吸积率估计不仅过度预测了黑洞的吸积率，而且还过度预测了邦迪半径本身的捕获率。最后，如果吸积反馈在本质上是突发的，那么文献中常规研究非辐射流的稳态假设可能不得不放弃。
We present numerical models of the gas dynamics in the inner parsec of the Galactic centre. We follow the gas from its origin as stellar winds of several observed young massive stars, until it is either captured by the central black hole, or leaves the system. Unlike our previous models, we include an outflow from the inner accretion flow. Two different kinds of outflows are modelled: (i) an instantaneous-response feedback mode, in which the outflow rate is directly proportional to the current black hole gas capture rate; and (ii) an outburst mode, which is stronger but lasts for a limited time. The latter situation may be particularly relevant to Sgr A*, since there is evidence that Sgr A* was much brighter in the recent past. We find that both types of outflow perturb the gas dynamics near the Bondi radius and the black hole capture rate significantly. The effects persist longer than the outflow itself. We also compare the effects of spherically symmetric and collimated outflows, and find that the latter are far less efficient in transferring its energy to the surrounding gas near the capture radius. Our results imply that accretion feedback is important for non-radiative accretion flows not only within but also outside the capture radius. Steady-state Bondi accretion rate estimates that do not account for feedback outflows over-predict not only the accretion rate onto the black hole but also the capture rate at the Bondi radius itself. Finally, the steady-state assumption under which non-radiative flows have been routinely studied in the literature may have to be abandoned if accretion feedback is bursty in nature.