Cooling and Star Formation in the Universe's Largest Galaxies

Voit博士和他的团队将探索在什么条件下星系团的热扩散气体可以过渡到不均匀的冷却和恒星形成。这些结果或许可以解释为什么星系不会无限膨胀。解析计算将探讨热气体的热稳定性如何取决于熵梯度。这些线性计算将用于测试已修改的流体力学代码，其中包括热传导。然后，这些代码将用于探索不稳定性的非线性增长，产生可以与真实星团的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低温气体在炽热的星系团介质中能存活多久，并计算出这些密集气体的预期光谱。模拟将在球对称和宇宙学生成的初始条件下运行。Voit博士和他的团队随后将研究在计算中包括热传导、磁流体动力学效应以及活跃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心区域的光学图像，这些样本已经在x射线中进行了研究，以探索中心星系内部和周围的恒星形成与热星系团气体状态的关系。研究生将通过参与研究而得到训练。Voit博士和他的合作者Donahue博士在研究生和本科生培训方面都有很好的记录。他们还共同撰写了一本重要的天文学入门教材，并将把这项研究的见解纳入未来的版本中。双方都将继续积极开展公共宣传活动。

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.