Testing Galactic-Wind Models With Observed Absorption-Line Kinematics

银河系风将等离子体、磁场和高能粒子从星系转移到它们周围的晕和星际介质中，并影响星系中恒星的形成速度。热气体、冷气体、宇宙射线和磁场是循环的观测成分。在一些恒星形成率相对较高的星系中，炽热的气体似乎正在将冷气体推向外，其规模是主星系的许多倍。然而，目前还不清楚光晕中有多少物质会逃脱银河系的引力，也不清楚有多少物质会回落到银河系。外流中热气成分的分析模型通常只考虑自由流动、恒速外流或辐射压力，但并不总是考虑来自大尺度热压、宇宙射线压力和磁场或星系旋转的气体驱动效应。这个项目旨在更好地理解冷气体的存在如何影响来自星系的热风和冲压风。这项工作建立了包括冷气体、热气体、宇宙射线和磁场在内的组件的外流动力学的半解析模型。然后，将模型预测与星系晕中冷气体运动学的观测进行比较。总体而言，这将提高我们对风动力学的理解，并提供逃逸各种星系的气体比例的估计。这些结果在解释其他天体物理领域的观测和理论模拟方面也有应用，在这些领域，关于银河系风的质量和能量损失率的知识对于理解其他星系属性非常重要，例如星系内和星际介质中的能量平衡。这个项目为学生的参与提供了两种不同的理论研究，一种专注于预测冷云运动学，另一种则预测来自各种风模型的可观察到的吸收模式。

Galactic winds transfer plasma, magnetic fields, and energetic particles from galaxies into their surrounding halos and to the intergalactic medium, and influence the star formation rate in galaxies. Hot gas, cool gas, cosmic rays, and magnetic fields are observed components that are circulated. In some galaxies with relatively high star-formation rates, hot gas seems to be pushing the cool gas outward over scales many times the size of the host galaxy. However, it is not clear how much matter in the halo will escape the galaxy's gravity, and how much matter will fall back to impact the galaxy. Analytic models for the hot-gas component of outflows usually consider only a free-streaming, constant velocity outflow, or perhaps radiation pressure, but gas-driving effects from large-scale thermal-pressure, cosmic-ray pressure and magnetic fields, or galactic rotation are not always included. This project aims to better understand how the presence of cool gas influences the thermal and ram-pressure driven winds from galaxies. This work builds a semi-analytic model for the outflow dynamics of components that includes cool gas, hot gas, cosmic rays, and magnetic fields. The model predictions are then compared to observations of cool gas kinematics in the halos of galaxies. Overall, this will improve our understanding of wind dynamics, and provide an estimate for the fraction of gas that escapes a variety of galaxies. The results have applications in the interpretation of observations and theoretical simulations in other astrophysical fields where knowledge about mass- and energy loss rates of galactic winds is important to understand other galactic properties such as the energy balance within galaxies and in the intergalactic medium. This project offers two different theoretical studies for student participation, one concentrating on predicting cool-cloud kinematics, and one predicting the observable absorption patterns stemming from variety of wind models.