The Star Formation Law in Nearby Galaxies

Erik Rosolowsky (University of Alberta)

February 11, 2019

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Abstract: Star formation governs the secular evolution of galaxies. Within galaxies, we usually describe star formation in terms of an empirical “law” that relates the local star formation rate to local conditions such as molecular gas density. While this model serves as a good first step, it breaks down beyond normal star-forming disk galaxies. In this talk, I will show how the EDGE-CALIFA survey of CO emission allows a new dissection of the star formation law using tools from the machine learning community. This analysis illustrates the strong role of the old stellar population at quenching star formation on a local scale. Unfortunately, the machine learning approach is empirical lacks a clear connection to the underlying physics. To understand the physical effects at work, I will show new results from the PHANGS survey, a large program with ALMA to map a 74 nearby galaxies at high (<100 pc) resolution. One immediate result we see from the PHANGS data is that the star formation efficiency per free-fall time is close to theoretical expectations (0.5%) and shows suggestive variations across the sample.