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arXiv 1402.4482astro-ph.GAastro-ph.CO
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在高红移盘星系模拟中活动星系核驱动的没有立即猝灭的外流

AGN-driven outflows without immediate quenching in simulations of high-redshift disk galaxies

Jared M. Gabor, Frédéric Bournaud

摘要:

我们利用高分辨率模拟的理想z=2孤立盘星系研究了活动星系核驱动的外流.幕式吸积事件导致外流速度>1000 km/s,质量外流速率高达恒星形成速率(几十个Msun/年)。外流风以大的张开角垂直于盘逃逸,并且通常是不对称的(即单极),因为在被解析的盘中活动星系核上方或下方的致密气体抑制了外流。由于吸积速率的快速变化,即使活动星系核实际上处于“关闭”状态,流出的气体也可能被探测到。“最高速度的外流有时,但不总是,集中在2-3千秒差距的银河系中心在峰值吸积。根据我们的纯热活动星系核反馈模型(以前文献中的标准模型),流出的物质大部分是热的(10^6 K)和扩散的(nH<10^(-2)cm-3),但包括夹带在热风中的冷组分。尽管有强大的爆发和高流出率,AGN反馈对星系盘中的致密气体几乎没有影响。因此,在我们的模拟中,活动星系核驱动的外流不会导致恒星形成的快速淬灭,尽管它们可能会去除大量的长(>Gyr)时间尺度的气体。

英文摘要:

We study outflows driven by Active Galactic Nuclei (AGNs) using high- resolution simulations of idealized z=2 isolated disk galaxies. Episodic accretion events lead to outflows with velocities >1000 km/s and mass outflow rates up to the star formation rate (several tens of Msun/yr). Outflowing winds escape perpendicular to the disk with wide opening angles, and are typically asymmetric (i.e. unipolar) because dense gas above or below the AGN in the resolved disk inhibits outflow. Owing to rapid variability in the accretion rates, outflowing gas may be detectable even when the AGN is effectively "off." The highest velocity outflows are sometimes, but not always, concentrated within 2-3 kpc of the galactic center during the peak accretion. With our purely thermal AGN feedback model -- standard in previous literature -- the outflowing material is mostly hot (10^6 K) and diffuse (nH<10^(-2) cm-3), but includes a cold component entrained in the hot wind. Despite the powerful bursts and high outflow rates, AGN feedback has little effect on the dense gas in the galaxy disk. Thus AGN-driven outflows in our simulations do not cause rapid quenching of star-formation, although they may remove significant amounts of gas of long (>Gyr) timescales.

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