Testing Galactic-Wind Models With Observed Absorption-Line Kinematics

星系风将等离子体、磁场和高能粒子从星系转移到它们周围的光晕和星系间介质中，并影响星系中恒星的形成速度。热气体、冷气体、宇宙射线和磁场是观测到的循环成分。在一些恒星形成率相对较高的星系中，热气体似乎将冷气体向外推，其规模是宿主星系的许多倍。然而，目前尚不清楚光晕中有多少物质会逃离星系的引力，又有多少物质会回落到银河系中。流出物热气体成分的分析模型通常只考虑自由流动、匀速流出或辐射压力，但不总是包括大规模热压、宇宙射线压力和磁场或星系旋转产生的气体驱动效应。这个项目旨在更好地理解低温气体的存在是如何影响来自星系的热风和夯压风的。这项工作建立了一个包括冷气体、热气体、宇宙射线和磁场在内的成分流出动力学的半解析模型。然后将模型预测与观测到的星系晕中的冷气体运动学进行比较。总的来说，这将提高我们对风动力学的理解，并提供对各种星系逃逸气体比例的估计。这些结果可以应用于其他天体物理学领域的观测和理论模拟的解释，在这些领域中，关于星系风的质量和能量损失率的知识对于理解其他星系特性（如星系内和星系间介质中的能量平衡）非常重要。这个项目提供了两种不同的理论研究供学生参与，一种集中于预测冷云的运动学，另一种预测来自各种风模型的可观测的吸收模式。

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.