APOGEE Observations of the Center of the Sagittarius dSph Galaxy
Abstract
As a system currently in the state of merging with the Milky Way -- and therefore a prototype for substructures that participate in the hierarchical build-up of our galaxy -- the structure of the Sagittarius (Sgr) dSph system is of particular interest. The APOGEE survey is ideally suited for the study of Sgr stars because of its ability to sample numerous stars over a large field of view; its high spectral resolution, which allows precision abundances and kinematics to be measured in these stars; and its infrared sensitivity, which allows these dust-extinguished fields to be explored more easily. Initial APOGEE observations of Sgr have provided accurate radial velocities, stellar parameters, and chemical abundances of over 200 confirmed Sgr members in the dwarf galaxy’s central 2.5 degrees. The < 1 km/s precision RVs have verified with strong significance the existence of a dynamical cold point in the center of the Sgr dSph. We explore various explanations for this phenomenon in terms of the distribution of both dark matter and stellar populations. The data also shows evidence of a metallicity gradient over the same radial range, demonstrating that the velocity dispersion variations span, and may be related to, differences in the distributions and dynamics of multiple stellar populations within the satellite.
- Publication:
-
American Astronomical Society Meeting Abstracts #221
- Pub Date:
- January 2013
- Bibcode:
- 2013AAS...22124201H