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Time: 2:30 pm
Location: ABB 102
Guest: Dr. Jiayi Sun
Department of Physics and Astronomy
Title: The PHANGS-ALMA Survey: 100,000 Molecular Clouds across the Local Universe
Molecular clouds are the building blocks of the cold interstellar gas and the immediate sights of star formation in galaxies. While they have been objects of study for many decades, it was only recently that our observing facilities become powerful enough to enable systematic surveys of molecular clouds over a large sample of galaxies in the local universe. I will give an overview of the PHANGS-ALMA project, our latest and greatest effort that maps and characterizes ~100,000 molecular clouds across ~90 nearby galaxies. We find that molecular clouds are much more diverse than people have once believed. They are very aware of their local environmental conditions and appear to be seamlessly integrated into the host galaxy ecosystem. In contrast to their short (~10 Myr) evolutionary timescale, they produce stars on a much longer (~Gyr) timescale, highlighting the inefficiency of the star formation process in the interstellar gas. Quantifying this inefficiency and comparing it to model predictions, we find tensions between the observations and a set of popular star formation theories, which signify that our current understanding of ISM evolution and star formation might still be incomplete.