Structure and Local Stability in Astrophysical Gas Dynamics

大尺度的气体动力学过程对于理解银河系的结构和演化是极其重要的。星系盘和晕中气体流动的不稳定性的发展可能会导致银河系中复杂的结构，这些结构可以在光学和无线电图像中直接看到。最终，最小尺度的结构会导致恒星的形成。总体而言，人们并没有很好地理解所看到的情况。在银河系高纬度看到的气体的来源是什么，为什么它似乎处于一种非常特殊的电离状态？热气体在盘中的命运是什么？在什么条件下，冷却的热凝结可以在动态活跃的流动中形成，从而产生所观察到的高速特征？为什么旋臂通常是凌乱的，有尖刺和树枝，但有些星系显示出精致的“宏伟设计”结构，而另一些星系则看起来完全混乱？利用这笔赠款进行的理论研究解决了上述问题。我们将研究天体物理气体流动的动力结构和稳定性。这些项目主要涉及对银河系尺度上的流动的研究，但在某些情况下，在更大的尺度上也有有趣和富有成效的应用。

Large-scale gasdynamical processes are extremely important to an understanding of the structure and evolution of the Galaxy. The development of instabilities in gas flows in the Galactic disk and halo may give rise to the intricate structures in the Galactic system that are seen directly in optical and radio images. Ultimately, structure on the smallest scales leads to star formation. By and large, what is seen is not well- understood. What is the origin of the gas seen at high Galactic latitude, and why does it seem to be in a very peculiar state of ionization? What is the fate of hot gas in the disk, and under what conditions can cool thermal condensations form in a dynamically active flow to give rise to the high velocity features which are observed? Why are spiral arms generally unkempt with spurs and branches often present, but with some galaxies showing an exquisite "grand design" structure while others appear completely chaotic? The theoretical research carried out with this grant addresses the questions posed above. The dynamical structure and the stability of astrophysical gas flows will be examined. The projects involve primarily studies of flows on a Galactic scale, but in some cases there are interesting and fruitful applications on larger scales.