Identifying RR Lyrae Variables and Globular Clusters in the Milky Way and Simulating Supermassive Black Hole Early Evolution

<div>This thesis presents four research projects about substructures of the Milky Way from large-sky surveys and supermassive black holes at high redshift in cosmological simulations. </div><div>First, I reported the searching result for globular clusters (GCs) associated with 55 Milky Way dwarf galaxies using Gaia DR2. Eleven candidates were identified and all were either known GCs or galaxies, yet only the six Fornax GCs were associated with the dwarf. The completeness of the GC search was above 90% for most dwarf galaxies and the 90% credible intervals on the GC specific frequency S_N were 12 < S_N< 47 for Fornax, S_N < 20 for the dwarfs with -12 < M_V< -10, S_N < 30 for the dwarfs with -10 < M_V< -7, and S_N < 90 for the dwarfs with M_V <-7. Based on S_N, I obtained that the probability of galaxies fainter than M_V = -9 to host GCs was lower than 0.1.</div>