The COMBS Survey II: Distinguishing the Metal-Poor Bulge from the Halo Interlopers.

2020 
The metal-poor stars in the bulge are important relics of the Milky Way's formation history, as simulations predict that they are some of the oldest stars in the Galaxy. In order to determine if they are truly ancient stars, we must understand the origins of this population. Currently, it is unclear if the metal-poor stars in the bulge ([Fe/H] 50\% probability of being bound to the bulge, and half are halo interlopers. We also see that the occurrence rate of halo interlopers increases steadily with decreasing metallicity across the full range of our sample (-3 < [Fe/H] < 0.5). Our examination of the kinematics of the confined compared to the unbound stars indicates the metal-poor bulge ([Fe/H] < -1 dex) comprises at least two populations; those confined to the boxy/peanut bulge and halo stars passing through the inner galaxy. We conclude that an orbital analysis approach, as we have employed, is important to uncover and understand the composite nature of the metal-poor stars in the inner region.
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