Modeling the Magellanic System: Insights into Galactic Accretion and Evolution

I present a novel pair of numerical models of the interaction history between the Large and Small Magellanic Clouds (LMC and SMC, respectively) and our Milky Way in light of recent high precision proper motions from the Hubble Space Telescope (Kallivayalil et al. 2006a,b). These proper motions imply that the Clouds are moving ∼100 km/s faster than previously considered. Using cosmologically motivated models for the dark matter halo of our Milky Way, these high speeds suggest that the Magellanic Clouds are on their first infall towards our Galaxy. I will show that a first infall scenario is consistent with cosmological expectations for high-speed LMC and SMC analogs identified in large-scale N-body simulations of structure formation (such as Millennium-II; Boylan-Kolchin et al. 2009). Additionally, I will show that the observed irregular morphology and internal kinematics of the Magellanic system (in gas and stars) are naturally explainable by interactions between the LMC and SMC, rather than gravitational interactions with the Milky Way. In particular, I will illustrate that the Magellanic Stream, a stream of HI gas trailing behind the Clouds 150 degrees across the sky, can be explained by the action of LMC tides on the SMC before the system has been accreted by the MW. I will also illustrate that the off-centered, warped stellar bar of the LMC and the pronounced differences in the kinematics of the gas and old stellar populations in the SMC are natural by-products of a recent direct collision between the SMC and LMC. A significant correlated burst of star formation is also expected in both galaxies at the time of this collision. Furthermore, SMC stellar debris tidally stripped during interactions with the LMC provides a natural explanation for the microlensing events observed towards the LMC by the MACHO and OGLE collaborations (Alcock et al. 2000; Wyrzykowski et al. 2011). Such stellar debris may be observable by upcoming deep optical surveys of the Magellanic Stream.;This thesis illustrates the significant role that dwarf-dwarf galaxy interactions can play in the evolution of these galaxies and may explain the dynamical state of a class of dwarf galaxies known as "Magellanic Irregulars".