Cooling and Star Formation in the Universe's Largest Galaxies

沃特博士和他的团队将探索星系团的热扩散气体可以过渡到不均匀冷却和恒星形成的条件。这一结果或许可以解释为什么星系不会无限变大。解析计算将探索热气体的热稳定性如何依赖于熵梯度。这些线性计算将用于测试已修改为包括热传导的流体力学代码。然后，这个代码将被用来探索不稳定性的非线性增长，产生可以与真实星系团的X射线观测相比较的模型。模拟将测试从星系中剥离出来的冷气体能在炎热的星系团介质中存活多久，并计算这些稠密气体的预期光谱。模拟将从球对称和宇宙产生的初始条件进行。然后，沃特博士和他的团队将研究在计算中包括热传导、磁流体力学效应以及活动星系核反馈到星系团气体中的能量将如何影响结果。该团队还将获得附近星系团样本中中央区域的光学图像，这些图像已被X射线研究，以探索中心星系及其周围的恒星形成如何与热星系团气体的状态有关。一名研究生将通过参与研究进行培训。沃特博士和合作者多纳休博士在研究生和本科生培训方面都有很好的记录。他们也是天文学入门的主要文本的合著者，并将把这项研究的见解纳入未来的版本中。两人都将继续积极参与公众宣传活动。

Dr Voit and his team will explore the conditions under which the hot diffuse gas of a galaxy cluster can make a transition to inhomogeneous cooling and star formation. The results may explain why galaxies do not grow indefinitely large. Analytic calculations will explore how the thermal stability of the hot gas depends on the entropy gradient. These linear calculations will be used to test a hydrodynamic code that has been modified to include thermal conduction. That code will then be used to explore the nonlinear growth of instabilities, producing models that can be compared with X-ray observations of real clusters. Simulations will test how long cool gas stripped from galaxies can survive as such in the hot cluster medium, and compute the expected optical spectra from those wisps of dense gas. Simulations will be run from both spherically-symmetric and cosmologically-generated initial conditions. Dr Voit and his team will then investigate how including thermal conduction, magnetohydrodynamic effects, and energy fed back into the cluster gas by active galactic nuclei in the calculation would affect the results. The team will also obtain optical images of the central regions in a sample of nearby galaxy clusters that have been studied in X-rays, to explore how star formation in and around the central galaxy is related to the state of the hot cluster gas. A graduate student will be trained by participation in the research. Dr Voit and collaborator Dr Donahue have a strong record of both graduate and undergraduate student training. They are also co-authors of a major text for introductory astronomy, and will incorporate insights from this research into future editions. Both will continue to be active in public outreach.