描述湍流多分量星系盘中的引力不稳定性
Characterizing gravitational instability in turbulent multi-component galactic discs
摘要：
引力不稳定性在星系演化和形成星际介质（ISM）中起着重要作用。ISM被观察到是高度湍流的，这意味着像气体表面密度和速度色散这样的可观测量取决于测量区域的大小。在这项工作中，我们调查，使用模拟的银河系一样的盘星系的分辨率为$\sim 9$ pc，在ISM湍流的性质，以及如何影响星系的引力稳定性。通过在稳定性分析中考虑到测量的密度和速度场的平均湍流标度，我们可以更鲁棒地描述星系稳定性的平均水平作为尺度的函数，并以直接的方式识别易于碎裂的尺度。此外，我们发现，反馈驱动的湍流光盘的稳定性可以很好地描述了“托姆”$Q$稳定性标准在所有尺度上，而经典的$Q$可以正式失去其意义上的小尺度，如果暴力光盘不稳定性发生在缺乏压力支持的模型从恒星反馈。
英文摘要：
Gravitational instabilities play an important role in galaxy evolution and in shaping the interstellar medium (ISM). The ISM is observed to be highly turbulent, meaning that observables like the gas surface density and velocity dispersion depend on the size of the region over which they are measured. In this work we investigate, using simulations of Milky Way-like disc galaxies with a resolution of $\sim 9$ pc, the nature of turbulence in the ISM and how this affects the gravitational stability of galaxies. By accounting for the measured average turbulent scalings of the density and velocity fields in the stability analysis, we can more robustly characterize the average level of stability of the galaxies as a function of scale, and in a straightforward manner identify scales prone to fragmentation. Furthermore, we find that the stability of a disc with feedback-driven turbulence can be well described by a "Toomre-like" $Q$ stability criterion on all scales, whereas the classical $Q$ can formally lose its meaning on small scales if violent disc instabilities occur in models lacking pressure support from stellar feedback.
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