Galactic Archaeology in the Local Group

Abstract

We are in the age of advanced surveys and simulations which have greatly expanded our understanding of the large scale evolution of the universe, but have also revealed many contradictions at small scale. Limitations of our simulations make it difficult to resolve faint substructures in Local Group analogs, hence we resort to observations which now drive our understanding of Galactic Archaeology. Large surveys are currently mapping the Milky Way and the Local Group, building up a panoramic view of stars to achieve a similar goal: understanding the history of the galaxies. This goal motivates this thesis, which combines multiple topics of research I undertook from 2017 to 2020. Starting inside the Milky Way, I will discuss the properties of the Galactic halo. We select the blue horizontal branch stars from the SkyMapper photometric survey, using it to trace the 3-dimensional stellar distribution, identifying substantial substructures. Following that, I will discuss the internal dynamics of the Large Magellanic Cloud (LMC). As the most prominent satellite in the Milky Way, the LMC plays a significant role in the Galactic evolution. We isolated different stellar populations in the LMC and compared their dynamical properties. Further, I will address the dynamical properties at the periphery of a globular cluster (GC) NGC3201. We measured the velocity gradient and dispersion and discussed the formation and evolution of this GC. In addition, I will present a discovery of a special stellar stream, whose progenitor is very likely to be a GC that sit below the metallicity floor. Beyond the Milky Way, I will discuss the potential formation process of the dwarf galaxies in the M31, whose distribution is strongly asymmetric. While this thesis consists of a number of broad topics surrounding the Galactic Archaeology, they all contribute to our understanding of galactic evolution.