Place: 4421 Sterling Hall, Coffee and cookies 3:30 PM, Talk begins 3:45 PM
Speaker: Betsy Mills, Brandeis University
Abstract: Star formation in environments from local molecular clouds to distant galaxies is characterized by a simple, linear relationship between the amount of gas compared to the amount of recently formed stars. However, star formation in the center of our Galaxy does not follow these universal scaling relations, suggesting that the star formation process has a more complex dependence on environment. In the Galactic center, scaling relations predict there should be a larger amount of star formation given the amount of dense gas that is present. My recent work has put new constraints on both these quantities, indicating that neither overestimates of gas density nor underestimates of star formation can completely account for this discrepancy. Instead, it is most likely that (1) in this environment there is a higher gas density threshold required for the onset of star formation and (2) the center of our galaxy is currently in a quiescent or low state in between cycles of starburst activity. This poses a challenge for using the Galactic center to better characterize deviations from star formation ‘laws’ in extreme environments, as the Galactic center is far from experiencing a global starburst. I describe two ways my recent work is addressing this challenge: firstly, by characterizing properties of dense gas and star formation in nearby starbursting nuclei at high spatial resolutions now available with ALMA. Secondly, I describe my recent studies of the Sgr B2 "mini-starburst”: an individual cloud in the galactic center that may be more characteristic of the global mode of star formation observed in nuclear starbursts. Finally, I end with a cautionary note on remaining challenges for correctly interpreting observations of dense gas tracers in more distant extreme and unresolved systems.