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arXiv 1104.3682astro-ph.GA
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大规模外流

Large--Scale Outflows in Galaxies

A. R. King, K. Zubovas, C. Power

摘要:

我们讨论了星系膨胀中的大规模外流,特别是由中央超大质量黑洞达到爱丁顿极限的吸积事件驱动的外流。我们表明,类星体辐射场康普顿-冷却的风冲击,直到这达到距离$\sim 1$ kpc的黑洞,但变得太稀,这样做在更大的半径。辐射过程不能在任何半径的流动时间内冷却冲击气体。因此,外流在小半径处是动量驱动的(这是解释$M - σ$关系所必需的)。在大半径,它们是能量驱动的,与最近的说法相反。我们解析地求解了中心源关闭后能量驱动壳层的运动。这表明冲击风中的热能可以驱动进一步的膨胀,持续的时间比中心源的活跃时间长$\sim 10$倍。在没有活动中心源的大半径处观察到的流出可能是由于该源的早期短(几百万年)活动阶段。

英文摘要:

We discuss massive outflows in galaxy bulges, particularly ones driven by accretion episodes where the central supermassive black hole reaches the Eddington limit. We show that the quasar radiation field Compton--cools the wind shock until this reaches distances $\sim 1$ kpc from the black hole, but becomes too dilute to do this at larger radii. Radiative processes cannot cool the shocked gas within the flow time at any radius. Outflows are therefore momentum-driven at small radii (as required to explain the $M - σ$ relation). At large radii they are energy-driven, contrary to recent claims. We solve analytically the motion of an energy--driven shell after the central source has turned off. This shows that the thermal energy in the shocked wind can drive further expansion for a time $\sim 10$ times longer than the active time of the central source. Outflows observed at large radii with no active central source probably result from an earlier short (few Myr) active phase of this source.

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