The Origins and Evolution of Molecular Clouds

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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.