Tidal streams in the Milky Way: an observational study
Powell, William Lee
The main focus of this dissertation is my observational study of the blue plume (BP) of the Canis Major Over-Density (CMa), a recently discovered statistical over-density of stars. In the discovery paper, Martin et al. (2004) claim that the CMa is the remnants of a dwarf galaxy that has been cannibalized by the Milky Way. This assertion was quickly challenged by other groups that claim that Martin et al. had instead just observed the signature of the warped and flared disk of the Milky Way, or perhaps previously unresolved spiral arm structure. My study set out to determine the true nature of the BP, and is the first effort that combined photometry and spectroscopy to study this population. There are two major results from this study. First, I detail a new method for dealing with differential reddening using young main sequence populations, and the total picture offered by combining photometry and spectroscopy. The second result is the measured distances, radial velocities, and stellar parameters for the stars of the BP. I will show conclusively that the BP of the CMa is unequivocally a manifestation of the warped disk of the Milky Way.