秒差距尺度活动星系核反馈的观测证据
Observational evidence for AGNs feedback at parsec scale
摘要：
在热的吸积流中，来自流最内部区域的辐射向外传播，并通过康普顿散射加热大半径处的电子。在以前的工作中已经表明，如果辐射足够强，$L\ga 2%L_{\rm Edd}$，在Bondi半径（$r_B\sim 10^5 r_s$）的电子将被加热到维里温度以上，从而吸积将停止。气体冷却后，吸积将恢复。这导致了黑洞活动的振荡。在本文中，我们表明，这种机制是一些紧凑的年轻射电源的间歇活动的起源。这种不确定性是解释这些来源的人口所必需的。我们计算了黑洞振荡的时间尺度，发现活动和非活动阶段的持续时间分别为$3\times 10^4 (0.1/α)(M/10^8\msun) (L/2%L_{\rm Edd})^{-1/2} {\rm yr}$和$10^5(α/0.1)(M/10^8\msun) {\rm yr}$，与解释观测所需的时间尺度一致。这种反馈在秒差距尺度下发生，在低光度活动星系核中是普遍存在的，在考虑它们的物质和能量输出时应该加以考虑。
英文摘要：
In a hot accretion flow, the radiation from the innermost region of the flow propagates outward and heats the electrons at large radii via Compton scattering. It has been shown in previous works that if the radiation is strong enough, $L\ga 2%L_{\rm Edd}$, the electrons at the Bondi radius ($r_B\sim 10^5 r_s$) will be heated to be above the virial temperature thus the accretion will be stopped. The accretion will recover after the gas cools down. This results in the oscillation of the black hole activity. In this paper we show that this mechanism is the origin of the intermittent activity of some compact young radio sources. Such intermittency is required to explain the population of these sources. We calculate the timescales of the black hole oscillation and find that the durations of active and inactive phases are $3\times 10^4 (0.1/α)(M/10^8\msun) (L/2%L_{\rm Edd})^{-1/2} {\rm yr}$ and $10^5(α/0.1)(M/10^8\msun) {\rm yr}$, respectively, consistent with those required to explain observations. Such kind of feedback occurring at parsec scale should be common in low-luminosity AGNs and should be considered when we consider their matter and energy output.
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