arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2006.05997astro-ph.GA
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用小尺度AGN风为银河系超级风提供动力

Powering galactic super-winds with small-scale AGN winds

Tiago Costa, Rüdiger Pakmor, Volker Springel

摘要:

我们提出了一个新的实现活动星系核(AGN)的反馈,通过小尺度,超快风的动网格流体动力学程序AREPO。根据现有的吸积盘风的约束条件,通过规定以超大质量黑洞为中心的球形边界上的质量、动量和能量通量来注入风。在清扫了与自己相等的质量后,小尺度风热化,为能量驱动的外流提供动力,结构和冷却特性与分析风的解决方案非常一致。动量驱动的解不容易出现,因为康普顿冷却半径通常比小尺度风的自由膨胀半径小得多。通过各种收敛性测试,我们表明,我们的实现产生风的解决方案,以及收敛到宇宙学模拟中实现的典型分辨率。我们测试我们的模型在孤立的银河系质量的星系的流体动力学模拟。在活动星系核的临界光度之上,最初的球形小尺度风为双极的能量驱动的超级风提供动力,这些超级风从星系核中爆发出来,以$> 1000 \rm \, km \, s^{-1}$的速度流向$\sim 10 \, \rm kpc$。这些能量驱动的外流导致恒星形成的温和但长期的减少,这在更高的AGN光度和更快的小尺度风中变得更加明显。恒星形成的抑制通过快速模式进行,包括去除密度最高的核气体,并通过一个缓慢的模式,有效地阻止晕气体吸积。我们的新实现使得有可能模拟活动星系核驱动的风在物理上有意义的和验证的方式在模拟星系演化,星际介质和黑洞吸积流。

英文摘要:

We present a new implementation for active galactic nucleus (AGN) feedback through small-scale, ultra-fast winds in the moving-mesh hydrodynamic code AREPO. The wind is injected by prescribing mass, momentum and energy fluxes across a spherical boundary centred on a supermassive black hole according to available constraints for accretion disc winds. After sweeping-up a mass equal to their own, small-scale winds thermalise, powering energy-driven outflows with dynamics, structure and cooling properties in excellent agreement with those of analytic wind solutions. Momentum-driven solutions do not easily occur, because the Compton cooling radius is usually much smaller than the free-expansion radius of the small-scale winds. Through various convergence tests, we demonstrate that our implementation yields wind solutions which are well converged down to the typical resolution achieved in cosmological simulations. We test our model in hydrodynamic simulations of isolated Milky Way - mass galaxies. Above a critical AGN luminosity, initially spherical, small-scale winds power bipolar, energy-driven super-winds that break out of the galactic nucleus, flowing at speeds $> 1000 \rm \, km \, s^{-1}$ out to $\sim 10 \, \rm kpc$. These energy-driven outflows result in moderate, but long-term, reduction in star formation, which becomes more pronounced for higher AGN luminosities and faster small-scale winds. Suppression of star formation proceeds through a rapid mode that involves the removal of the highest-density, nuclear gas and through a slower mode that effectively halts halo gas accretion. Our new implementation makes it possible to model AGN-driven winds in a physically meaningful and validated way in simulations of galaxy evolution, the interstellar medium and black hole accretion flows.

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