Spectroscopic Explorations of Milky Way Stellar Populations

Stellar spectroscopy is a fundamental tool to investigate the dynamics and chemistry of stellar populations in the Milky Way. In this thesis, we present radial velocities and metallicities of giant stars in the disk and halo obtained through low-resolution spectroscopy (R ∼ 2, 000–2, 500) to undertake two focused studies.

Using spectroscopic data of M-giants, in addition to photometric and astrometric data, we have traced the tidal tails of the Sagittarius dwarf galaxy across the Northern and Southern Hemispheres. We compare these data to N-body simulations available in the literature to place constraints on the shape of the dark matter halo. As a critical tool in this enterprise, we present a modification to the near-IR calcium triplet metallicity determination method, which traditionally requires a priori knowledge of stellar distance to derive the stellar metallicities of RGB stars. The modified method provides a new tool to measure the metallicities of stars of unknown distances, and we apply it to stars along the tidal tails of Sagittarius.

In a separate study, we present measurements of the Solar motion and the Local Standard of Rest as derived from the observed kinematic of K-giant stars in the Grid Giant Star Survey.

Finally, we describe contributions made to the construction of the APOGEE-2S spectrograph, as a result of my work in the IR instrumentation team at the UVa Department of Astronomy.