Chemodynamics of the Galactic Halo

Abstract

Following the launch of the Gaia satellite, providing data for well over a billion stellar objects, the study of our home galaxy has evolved into a data-driven science. The Galaxy now acts as an environment in which we can employ novel data-driven techniques, while still maintaining a deep link with the classical mathematical tools developed prior to the 21st century. To complement the data, there exists frameworks for developing both large N-body and smaller tailored simulations of galaxies which allow us to test unsolved questions. In this PhD dissertation, I present research from six published or submitted first-author papers that speak to a wide variety of these aspects of Milky Way science, which is now commonly referred to as Galactic Archaeology. Chapter 1 introduces all the core concepts necessary to understanding the science and results presented in this thesis. This includes a brief introduction to general galaxy formation, an overview of the Milky Way, an introduction to the mathematical tools of galactic dynamics, and a description of some more modern computational tools. The primary focus of chapter 2, 3 and 4 is the connection between the Milky Way's most recent major merger and other structure in the galaxy. Namely, how dark matter subhaloes, the bar, and the Large Magellanic Cloud can influence the phase space characteristics of the merger debris. Chapters 5 and 6 explore the dynamics of one of the Milky Way's main dwarf galaxies -- the Sagittarius dwarf spheroidal. Specifically I look to explain the origin of bifurcation of the Sagittarius stream in addition to the origin of one of Sagittarius' globular clusters. Following this, chapter 7 examines the application of non-negative matrix factorisation to the chemical and kinematic space of stars in the stellar halo. This is done to categorise the halo into in-situ and ex-situ. Lastly, chapter 8 summarises and re-contextualises these papers, and details future work.