探索在盘的外围作为星际turbulence源的云状气体吸积
Exploring cloudy gas accretion as a source of interstellar turbulence in the outskirts of disks
摘要：
本文对扩展HI银盘中的凝块气体持续注入效应进行了高分辨率2D-MHD数值模拟。给定一定的吸积率，盘的响应取决于其表面气体密度和温度。对于银河系在~20 kpc的银河系中心距离的条件下，和质量吸积率符合目前的经验和理论测定在银河系中，雨的紧凑的高速云到磁盘上可以维持跨音速湍流运动在温暖的阶段（~2500 K）的HI。因此，HI线宽预计为~6.5 km/s的气体层在2500 K，如果下降是唯一的驱动湍流的机制。这封信中给出了由此产生的强迫流的一些统计特性。还讨论了气体速度弥散的径向依赖性。
英文摘要：
High--resolution 2D--MHD numerical simulations have been carried out to investigate the effects of continuing infall of clumpy gas in extended HI galactic disks. Given a certain accretion rate, the response of the disk depends on its surface gas density and temperature. For Galactic conditions at a galactocentric distance of ~20 kpc, and for mass accretion rates consistent with current empirical and theoretical determinations in the Milky Way, the rain of compact high velocity clouds onto the disk can maintain transonic turbulent motions in the warm phase (~2500 K) of HI. Hence, the HI line width is expected to be ~6.5 km/s for a gas layer at 2500 K, if infall were the only mechanism of driving turbulence. Some statistical properties of the resulting forcing flow are shown in this Letter. The radial dependence of the gas velocity dispersion is also discussed.
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