A Masing BAaDE’s Window
Ylva Pihlström, University of New Mexico
Evolved, intermediate mass stars are tracers of an intermediate age stellar population. Due to high mass-loss rates, they harbor circumstellar envelopes, in which different types of molecular maser emission can be observed. The maser emission allows not only studies of the physical conditions in the circumstellar envelope itself, but also can be used to test Galactic dynamics. Both these facets are investigated in the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey, using 28,000 SiO maser emitting stars in the Milky Way galaxy observed by the VLA and ALMA. I will give an overview of this survey and discuss a few of our results and challenges: A marginal flux bias exists in our sample due to two different sets of frequencies observed, which could partly be corrected for using longer integration times at ALMA. We have collected an extensive infrared data set for our sample, providing a means of modeling parameters such as bolometric luminosities and mass loss rates. Infrared colors further helps to separate C-rich from O-rich stars, and may also be tied to line ratios, tying back to the conditions in the circumstellar envelope.