The Origins and Evolution of Molecular Clouds

所有的恒星和行星系统都是在寒冷而黑暗的氢分子云中形成的。恒星形成的过程产生了高质量的恒星，它们的辐射和恒星风破坏了它们的宿主分子云。因此，在我们银河系的生命周期中，持续的恒星形成需要不断形成新的分子云。尽管对恒星形成过程进行了数十年的研究，但对分子云的形成以及这些云的结构如何决定什么样的恒星将形成知之甚少。分子云演化有几种理论，但很少有观测限制来约束推测。我们知识上的这一缺陷代表了我们理解宇宙起源的最大差距之一。这笔拨款将通过资助研究来确定驱动分子云形成及其随后的恒星形成的物理因素，直接解决这一差距。我的研究小组将通过三种不同的途径来解开这个谜团。首先，我们将使用超级计算机模拟许多不同分子云的演变，每个分子云都有独特的物理效应组合，如磁场强度或湍流气体运动。通过使用新颖的图像处理方法，我们将这些结果与真实的云进行比较，并找出哪一组物理最能再现真实的云。其次，我们将使用智利新的阿塔卡马大型毫米/亚毫米阵列来检查10个附近星系的分子云种群。通过利用对其他星系的“自上而下”视角，我们可以在整个星系的背景下研究这些云。这项研究将确定星系环境如何影响分子云的演化和恒星的形成。最后，我们将研究遥远的星系，在那里，望远镜的低分辨率将许多云混合在一起。有了从以前的观测中获得的知识，我们将能够解释60个星系的观测结果，以了解分子气体在各种星系类型中是如何不同地演化的。因此，我们将进行明确的观察，以确定控制分子云形成和演化的过程。

All stars and planetary systems form in cold and dark clouds of molecular hydrogen. The process of star formation births high mass stars whose radiation and stellar winds destroy their host molecular clouds. Thus, continued star formation over the lifetime of our Galaxy requires the ongoing formation of new molecular clouds. Despite decades of studying the star formation process, very little is known about molecular cloud formation and how the structure of those clouds determines what kind of stars will form. There are several theories of molecular cloud evolution, but few observational limits to constrain speculation. This deficit in our knowledge represents one of the largest gaps in understanding our cosmic origins. This grant will directly address this gap by funding research to identify the physical agents that drive the formation of molecular clouds and their subsequent star formation. My research group will approach this mystery using three different avenues. First, we will use supercomputers to simulate the evolution of many different molecular clouds, each with a unique mix of physical effects such as magnetic field strength or turbulent gas motions. By using novel image processing methods, we will compare these results to real clouds and find which set of physics best reproduces real clouds. Second, we will examine the populations of molecular clouds in ten nearby galaxies using the new Atacama Large Millimetre/Submillimetre Array in Chile. By taking advantage of the "top-down" perspective on other galaxies, we can study these clouds in the context of an entire galaxy. This study will establish how the galactic environment influences molecular cloud evolution and star formation. Finally, we will study distant galaxies, where the poor resolution of telescopes blends many clouds together. With knowledge gained from previous observations, we will be able to interpret observations of 60 galaxies to understand how molecular gas evolves differently across the wide variety of galaxy types. We will thus make definitive observations to identify which processes govern molecular cloud formation and evolution.