Name/Affiliation: John Bochanski (Haverford College/Rider University)
The Most Distant Stars in the Milky Way: Confirmation of an M giant near the Galaxy's Virial Radius
We have assembled a sample of over 400 M giant candidates from UKIDSS and SDSS, spread over 2,400 sq. deg. Our spectroscopic follow-up campaign has identified nine M giants to date. Here, we report on the spectroscopic confirmation of an M giant in the outer halo of the Galaxy, at a distance of > 180 kpc. The star was previously identified as an M giant candidate based its near-infrared and optical colors, and its lack of any measurable proper motion. The M giant was confirmed using optical spectroscopic features, and has a heliocentric radial velocity of ~ -60 km/s. It is the most distant Milky Way star found to date, and is likely the result of accretion in the outer halo. We discuss the likely scenarios for its formation, and the implications of distant halo giants on the evolution of the Milky Way's halo.