旋转星系冕的热不稳定性
Thermal instability in rotating galactic coronae
摘要：
通过线性微扰分析研究旋转、分层、非磁化大气的热稳定性，发现稳定性、超稳定性或不稳定性，这取决于气体分布的性质，但也取决于微扰的性质。在相关的情况下，向外增加的比熵和角动量的分布，轴对称扰动指数增长，除非它们的波长足够短，他们是由热传导阻尼;非轴对称扰动通常经历过稳定的振荡在零电导率的限制，但有效地稳定的热传导，提供旋转是微分。在某种程度上，所研究的模型代表了盘状星系的热大气约束不良，这些结果意味着，斑点状的，冷的超密度不太可能在星系日冕中增长，这表明银河系的高速云的外部起源。
英文摘要：
The thermal stability of rotating, stratified, unmagnetized atmospheres is studied by means of linear-perturbation analysis, finding stability, overstability or instability, depending on the properties of the gas distribution, but also on the nature of the perturbations. In the relevant case of distributions with outward-increasing specific entropy and angular momentum, axisymmetric perturbations grow exponentially, unless their wavelength is short enough that they are damped by thermal conduction; non-axisymmetric perturbations typically undergo overstable oscillations in the limit of zero conductivity, but are effectively stabilized by thermal conduction, provided rotation is differential. To the extent that the studied models are representative of the poorly constrained hot atmospheres of disc galaxies, these results imply that blob-like, cool overdensities are unlikely to grow in galactic coronae, suggesting an external origin for the high-velocity clouds of the Milky Way.
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