APOGEE Constraints on the Origin of the Metal-Rich Halo
Matthew Shetrone - University of Texas
The Apache Point Observatory Galactic Evolution Experiment (APOGEE) has observed more than 300,000 giants across all components of the Milky Way. A significant fraction of these giants have been found to be metal-poor but determining to which galactic component these stars belong is a significant problem. By combining the APOGEE abundances with GAIA-TGAS proper motions and models of galactic structure, we are able to separate out relatively clean samples of thin, thick, and halo metal-poor samples. However, the metal-poor halo does not seem to be a single population and the only slightly metal-poor inner halo has many similarities to the thick disk and bulge populations while the outer halo has a chemical evolutionary history similar to the Sagittarius and Magellanic dwarf galaxies. By combining information from APOGEE and lessons learned from Kepler asteroseismology, we place constraints on the origin of the inner and outer halo and make suggestions for directions for further exploration of galactic chemical and dynamical modeling.
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