Book Description

How do low-mass galaxies grow into massive spirals like our Milky Way? How does cold gas reach the inner disks of galaxies to feed ongoing star formation? These are some of the fundamental outstanding questions in galaxy formation and evolution. The Magellanic System holds the key to answering these questions. This system consists of the Large and Small Magellanic Clouds (LMC and SMC), which are the closest example of interacting dwarf galaxies to us, and the Magellanic Stream; an extensive complex of cold and ionized gas that surrounds them. While the Magellanic System contains unambiguous evidence of gas accretion and galaxy interactions, its origin is still unexplained by current models. The LMC is uncommon among late-type galaxies because its stellar bar appears offset from its stellar disk. In addition, the Magellanic Stream is highly ionized, unexpectedly massive, and composed of material from both the LMC and SMC. Finally, there are claims of dwarf satellite galaxies aligned with the Magellanic Stream and the Clouds that support the notion that these dwarf galaxies might have arrived in the Milky Way with the LMC and SMC. In my thesis, I tackle these mysteries of the Magellanic System. My results clarify the origin and properties of the offset between the stellar bar and disk by showing that it is a long-lived feature that arises from the gravitational interaction between the LMC and the SMC. This result matches observational evidence of the tidal interaction between the LMC and SMC, and has implications for our measurements of other galaxies across the universe. My results also elucidate how this tidal interaction between the Clouds can strip gas from both the LMC and SMC into a long stream that both leads and trails the Clouds on the sky. This work makes predictions, which will be tested in future surveys, for the chemical abundances in the Leading Arm of the Stream. The Clouds' interaction history and their proximity to us suggest that they have undergone significant tidal stripping and may have been much more massive in the past. My work demonstrates how an LMC that was more massive would bring a significant amount of warm gas as it fell into the Milky Way. This gas will be the source of the missing ionized component of the Stream required to match the observations. Finally, I hypothesize the number of satellite dwarf galaxies that are expected to arrive with this massive LMC by examining analog galaxies in cosmological simulations. This result also has implications for our understanding of the satellite galaxy population of the Milky Way. This is a complete picture of the Magellanic System where the LMC entered the Milky Way as the largest galaxy of a group of dwarf galaxies with its own bound gas. The interactions between the LMC and SMC in this Magellanic Group combined with ram-pressure stripping from the Milky Way's hot halo create the long, high-mass Stream of ionized and neutral gas. The lessons we learn from the Magellanic Clouds will help us understand galaxy formation and evolution across the universe.