The Milky Way in SDSS and in N-body Models

Abstract

In this thesis, I present a comparison between recent Sloan Digital Sky Survey (SDSS) Galactic studies and N-body simulations to aid in the interpretation of observed structural features. I investigate the origin of the Galactic thin/thick disk system and the contents of the Galactic halo by drawing comparisons to two high resolution simulations produced using GASOLINE. My aim is twofold: (1) to assess the plausibility of radial migration as a main driver for shaping the thick disk, and (2) to evaluate via Jeans equations properties of the Galactic potential within the SDSS volume. I arrive as several key findings: 1. Radial migration can produce on a global scale a physically reasonable thin/thick disk system in an N-body simulation. 2. Secular evolution via radial migration could be the source of spatial, chemical and kinematic disk trends observed in the solar cylinder by SDSS. 3. Jeans equations can meaningfully recover mean accelerations from a non steady-state, non axisymmetric cosmologically derived N-body simulation. 4. The morphology of the acceleration maps generated using Jeans equations applied to SDSS data is consistent with the presence of dark matter and inconsistent with a baryon only model of the Milky Way. 5. An analytic technique utilizing Jeans equations can meaningfully recover an N-body simulation's mean dark matter axis ratio. 6. The same analytic technique applied to SDSS Galactic halo data indicates the Milky Way dark matter axis ratio within the SDSS volume is qDM=0.47 ± 0.14. Breakthroughs such as these were enabled by recent rapid progress in both observational surveys and simulation science. This thesis demonstrates the emergent and informative value of direct comparison between the two.