Quasar反馈：更多的爆炸为您的巴克
Quasar Feedback: More Bang for Your Buck
摘要：
我们提出了一个两阶段模型的反馈效应，从一个明亮的类星体上的冷气体在星系。来自吸积盘附近的反馈很难直接撞击~kpc的致密分子云。但是，如果这样的反馈可以驱动一个弱的风或外流在热，弥漫ISM（一个相对“容易”的任务），然后在这样的外流经过冷云，不稳定性的组合将驱动云的材料，以有效地扩大在垂直于外流的方向。这种膨胀极大地增加了云物质的有效截面，使其更容易受到电离和动量耦合的影响，这些都是由于吸收了入射的类星体辐射场。即使是这种性质的中等影响，也能极大地改变云在大半径处完全电离的能力，并被辐射压驱动成二次外流。由于可以被观测到的类星体辐射场电离的动量和体积的量足以影响整个冷气体供应，一旦它以这种方式被改变（“初始”反馈只需要在低密度热气体中引发适度的风），这将减少一个数量级的反馈所需的能量预算来影响宿主星系。如果初始反馈必须直接加热或吹出银河系气体，则需要约5%的辐射能量（约100%动量），如果只有约0.5%的光度（约10%动量）可以耦合驱动初始热流出，则这种机制可能是有效的。这意味着从吸积盘附近流出的热气流率仅为BH吸积率的5-10%。
英文摘要：
We propose a two-stage model for the effects of feedback from a bright quasar on the cold gas in a galaxy. It is difficult for feedback from near the accretion disk to directly impact dense molecular clouds at ~kpc. But if such feedback can drive a weak wind or outflow in the hot, diffuse ISM (a relatively 'easy' task), then in the wake of such an outflow passing over a cold cloud, a combination of instabilities will drive the cloud material to effectively expand in the direction perpendicular to the outflow. Such expansion dramatically increases the effective cross section of the cloud material and makes it more susceptible to ionization and momentum coupling from absorption of the incident quasar radiation field. Even a moderate effect of this nature can dramatically alter the ability of clouds at large radii to be fully ionized and driven into a secondary outflow by radiation pressure. Since the amount of momentum and volume which can be ionized by observed quasar radiation field is more than sufficient to affect the entire cold gas supply once it has been altered in this manner (and the 'initial' feedback need only initiate a moderate wind in the low-density hot gas), this reduces by an order of magnitude the required energy budget for feedback to affect a host galaxy. Instead of ~5% of the radiated energy (~100% momentum) needed if the initial feedback must directly heat or blow out the galactic gas, if only ~0.5% of the luminosity (~10% momentum) can couple to drive the initial hot outflow, this mechanism could be efficient. This amounts to hot gas outflow rates from near the accretion disk of only 5-10% of the BH accretion rate.
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