Toward a New Understanding of the Relationship between Dense Gas and Star Formation in the Center of our Galaxy and the Distant Universe

Date: 
Wednesday, February 08, 2017 - 3:30pm to 4:30pm PST
Speaker: 
Betsy Mills
Affiliation: 
San Jose State University
Location: 
N232, Room 103
Event Type: 
Colloquium

An extreme environment for star formation, the center of our Galaxy is observed to have many properties in common with those of high-redshift galaxies. As our best local analog for these sources, it provides a unique opportunity to probe detailed gas properties and their impact on star formation at a spatial resolution that is unobtainable at the high redshifts of the peak of star formation and galaxy assembly. In this talk, I will focus on efforts to accurately measure the total gas reservoir, and constrain how its density and temperature vary, as these are critical for understanding both star formation efficiency, and whether star formation proceeds differently than the local norm. I will first present new and more accurate density measurements in the Galactic Center using observations of HC3N and discuss what they tell us about the current lack of star formation seen in this region. As relatively faint tracers like HC3N are not typically available in distant and high redshift extragalactic sources, I will then discuss new work on the bright and commonly-used tracer HCN in the Galactic center. We identify several systematic deviations from the relationship between gas mass and the brightness of HCN 1-0 that suggest a need to recalibrate this tracer for use in the most extreme environments in order to accurately recover total dense gas mass present and correctly interpret its link to star formation using the Gao-Solomon relation. Finally, I will present a new study of H2 rotational lines toward the very center of our Galaxy that tests another method of accurately recovering the total gas mass present in extreme environments.

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