Astro Seminar - Mike Rich

Title:  The Blanco DECam Bulge Survey:  A Panchromatic Window on the Galactic Bulge

Abstract:

The development of wide field imaging cameras on large optical telescopes has opened a new opportunity to examine stellar populations over the full optical/near-IR passband.  We have used the Dark Energy Camera on the Blanco 4m telescope to image 200 sq. deg of the Galactic bulge in the Rubin/LSST passbands of ugrizY.   The use of the u band gives a new calibration of red clump star metallicities to a precision of ~0.2 dex, and the use of the u band to observe and study multiple populations in many of the globular clusters in the BDBS footprint.  We show that some claims for extremely young stellar populations in the Galactic bulge cannot be supported.  We also find that the bulge divides into two abundance distributions- one similar to the one-zone model of chemical evolution near the Galactic plane, and the other a more metal poor distribution, outside of 500 pc.  We also find that the structure of the bulge as a function of metallicity is stratified parallel to the plane and previous claims for a spheroidal distribution for giants with [Fe/H]<0 are not sustained.  We will discuss the future science being undertaken as our sample is integrated with Gaia astrometry. I will discuss the implications for the formation history of the bulge.