SiO Masers in the Galactic Bulge and Disk: Kinematics from the BAaDE Survey
Abstract
We present the first results from the Bulge Asymmetries and Dynamic Evolution (BAaDE) survey. Though only a subset of the complete survey (∼2700 out of ∼20,000 final sources), our data comprise the largest radio kinematic survey to date of stellar SiO masers observed toward the Galactic bulge and plane from -15° < l < +12° and -6° < b < +6°. Our sources include a substantial number of line-of-sight velocities in high extinction regions within ±1° of the Galactic plane. When matched with 2MASS photometry, our radio-detected sample lies significantly brighter than and redward of the first red giant branch tip, reaching extremes of (J - Ks)0 > 8, colors consistent with Mira variables and mass-losing AGB stars. We see a clean division into two kinematic populations: a kinematically cold (σ ∼ 50 km s-1) population that we propose is in the foreground disk, consisting of giants with 2MASS Ks < 5.5, and a kinematically hot (σ ∼ 100 km s-1) candidate bulge/bar population for most giants with Ks > 5.5. Only the kinematically hot giants with Ks > 5.5 include the reddest stars. Adopting 8.3 kpc to the Galactic center, and correcting for foreground extinction, we find that most of the sources have M bol ∼ -5, consistent with their being luminous and possibly intermediate-age AGB stars. We note some tension between the possible intermediate age of the kinematically hot population, and its high-velocity dispersion compared to the disk.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 2018
- DOI:
- arXiv:
- arXiv:1805.04522
- Bibcode:
- 2018ApJ...861...75T
- Keywords:
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- Galaxy: bulge;
- Galaxy: kinematics and dynamics;
- stars: AGB and post-AGB;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 18 pages, 17 Figures