The Bulge Asymmetries and Dynamics Survey of the Galactic Plane

R. Michael Rich (UCLA)
Friday, April 19, 2019 - 12:15pm to 1:00pm

A fraction of AGB stars produce SiO maser emission that can penetrate any dust.  Recent advances in observational strategy enable the detection of thousands of these sources, with the maser line being used to measure a radial velocity. We have shown that the SiO maser AGB population in the Plane divides into cold and hot kinematic subpopulations, with the hot population associated with the bulge and following its kinematics; a subset are also associated with long period Mira variables.   We also find that the bolometric luminosities of the masers are typically <-5, raising the possibility that many are evolved from an intermediate age stellar population.  Such a stellar population is seen in microlensed bulge dwarfs, but is not detected in deep HST color-magnitude diagrams of bulge fields.  This population has not been studied by APOGEE and is mostly undetected in Gaia (due to the red colors and low Galactic latitudes).   I will discuss this result and other recent results of interest in the Galactic bulge.

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