Program: GS-2008B-Q-19

Though it is now clear that accretion of dwarf galaxies likely played a prominent role in creating the Milky Way (MW) halo, the chemical abundance patterns of current MW satellites are distinct from those of halo stars. The star formation histories and internal dynamics in surviving dwarf galaxies have been very different from the conditions experienced by the Milky Way halo and thin and thick disks over the last 8-10 Gyr and have resulted in characteristic abundance patterns in Milky Way populations when compared to those in dwarf galaxies. Through the technique of ``chemical fingerprinting" it is possible to identify tidally stripped and captured stars moving through the Galactic field based on these abundance signatures, and even determine the specific formation site of individual stars. This project will carry out such chemical fingerprinting on members of the so-called Galactic Anticenter Stellar Structure (GASS) that has been identified both as a possible tidal stream from an accreted dwarf galaxy, or a warp of the Milky Way disk. Quantitative chemical abundances of a properly selected set of elements will be used to determine whether this sample of GASS stars has abundance patterns that are typical of a dwarf galaxy or of the Galactic disk.