论文标题
宇宙射线穿过星形的星系序列。 II：稳定性限制和宇宙射线驱动流出的发作
Cosmic rays across the star-forming galaxy sequence. II: Stability limits and the onset of cosmic ray-driven outflows
论文作者
论文摘要
宇宙射线（CRS）是一种合理的机制，用于从星形星系的光盘发射凉爽的材料风。但是，关于哪种类型的星系可能寄主CR驱动的风，或这些风在调节星系的恒星形成率中起着什么作用，尚无共识。利用本系列上一篇论文中开发的HADRONIC CRS的运输和损失的详细处理，在这里我们开发了一种半分析模型，该模型使我们能够评估使用CRS从银河盘发射凉风的可行性。特别是，我们确定了临界Cr通量（以及相应的恒星形成速率表面密度），在该临界液通量中，由于CRS在风中驱动气体或以其他方式使其不稳定，因此排除了给定星系内的静水平衡。我们表明，对于具有典型的星系和局部矮人气体表面密度的恒星形成星系，此Cr稳定性曲线的座位巡逻于肯尼古特 - schmidt参数速度与气体表面密度相对于气体表面密度的肯尼卡特 - schmidt参数空间中观察到的星系分布的高侧。然而，守望者损失使CRS无法在表面密度较高的星系中驱动风。我们的结果表明，像银河系这样的静态，低表面密度星系在不稳定性的风口峰上固执，因此，对ISM参数的微小变化可以导致CR驱动的流出量的发射，因此，我们建议CR反馈对大多数现代星系的星星形成效率构成了最终的极限限制。
Cosmic rays (CRs) are a plausible mechanism for launching winds of cool material from the discs of star-forming galaxies. However, there is no consensus on what types of galaxies likely host CR-driven winds, or what role these winds might play in regulating galaxies' star formation rates. Using a detailed treatment of the transport and losses of hadronic CRs developed in the previous paper in this series, here we develop a semi-analytic model that allows us to assess the viability of using CRs to launch cool winds from galactic discs. In particular, we determine the critical CR fluxes -- and corresponding star formation rate surface densities -- above which hydrostatic equilibrium within a given galaxy is precluded because CRs drive the gas off in a wind or otherwise render it unstable. We show that, for star-forming galaxies with lower gas surface densities typical of the Galaxy and local dwarfs, the locus of this CR stability curve patrols the high side of the observed distribution of galaxies in the Kennicutt-Schmidt parameter space of star formation rate versus gas surface density. However, hadronic losses render CRs unable to drive winds in galaxies with higher surface densities. Our results show that quiescent, low surface density galaxies like the Milky Way are poised on the cusp of instability, such that small changes to ISM parameters can lead to the launching of CR-driven outflows, and we suggest that, as a result, CR feedback sets an ultimate limit to the star formation efficiency of most modern galaxies.
