Events Calendar
Circumstellar SiO Masers in the Bulge Asymmetries and Dynamical Evolution Survey
Monday June 10, 2019
| 1:00 pm
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Presenter: | Michael Stroh |
|---|---|---|
| Series: | Thesis and Dissertation Defenses | |
| Abstract: | The Bulge Asymmetries and Dynamical Evolution (BAaDE) survey aims to explore the complex structure of the inner Galaxy and Galactic Bulge, by using the 43 GHz receivers at the Karl G. Jansky Very Large Array (VLA) and the 86 GHz receivers at the Atacama Large Millimeter/submillimeter Array (ALMA) to observe SiO maser lines in red giant stars. The goal is to construct a sample of stellar point-mass probes that can be used to test models of the gravitational potential, and the final sample is expected to provide at least 20,000 line-of-sight velocities and positions. The SiO maser transitions occur at radio frequencies, where extinction is negligible, thus allowing a dense sampling of line-of-sight velocities in the most crowded regions of the Milky Way. In the ALMA sample, a 71% detection rate of SiO masers is obtained, which increases to 80% when considering only the likely oxygen-rich stars in our sample. In addition to SiO, emission from carbon-bearing molecular transitions is detected in a small subset of the sample. Based on Galactic locations and kinematical associations, the extent of the emission, and infrared colors, we are able to classify a significant fraction of our carbon-molecule detections as likely young stellar objects. Further, since the primary aim of the BAaDE survey is to use stars as point-mass velocity probes, I will discuss possible biases in our derived line-of-sight velocities, as well as a possible distance-sensitive bias between 43 GHz and 86 GHz detected samples. I will compare the relative SiO line strengths and their agreement with current pumping models, which suggest the SiO line strengths can trace the changing conditions within the circumstellar envelopes. I present an analysis of SiO masers from OH/IR stars in the BAaDE survey, since OH/IR stars should have thicker circumstellar densities than the Mira-like stars that likely dominate the BAaDE population. Finally, I will introduce a monitoring campaign of 43 GHz SiO masers in the BAaDE sample, with the aim of deriving variations in SiO line ratios and line strengths as a function of stellar phase. | |
| Host: | Ylva Pihlström | |
| Location: | PAIS-2540, PAIS | |
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