Date: Friday 04-Apr-2014
Speaker: Dr. Elisabeth Mills (NRAO)
Title: Extreme (and not so extreme!) gas in the center of the Galaxy
Gas in the central parsecs of our Galaxy is subject to a harsh environment, including the close proximity of a supermassive black hole, supernova remnants, and massive star clusters. By characterizing the molecular gas conditions in this region, we can quantify the effect that the resulting shocks, x-rays, and cosmic rays have on gas properties and eventually star formation in this region. I will present a combination of results from the APEX, VLA, and GBT telescopes which place new limits on the large densities, temperatures, and turbulent line widths found in the molecular gas in the central 100 parsecs. Close to the black hole, we use data from the APEX telescope, to study the gas density in the Circumnuclear disk (CND), finding that it is not stable against tidal disruption. Almost all clumps appear to be transient and unlikely to form stars. We additionally find that reprocessed dust radiation from the central cluster appears to be contributing to radiative excitation of HCN in the CND, which may lower the gas densities inferred using this molecule. Farther from the black hole, I will present larger scale VLA and GBT surveys of gas temperatures and turbulence in Galactic center clouds, including new detections of a 400 K gas component which may be shock heated, and finally new hints of cooler and less turbulent clumps embedded within these clouds.
Date: Monday 05-May-2014
Speaker: Dr. Nick Indriolo (Johns Hopkins University)
Title: Herschel Survey of OH+, H2O+, and H3O+ in Galactic Sight Lines: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
