Near Field Cosmology with Milky Way's Satellite Galaxies and Stellar Streams

银河系的外晕是宇宙中了解星系形成和演化以及暗物质本质的最佳地点之一。特别是，当最近的天基（如盖亚）和地面（如暗能量调查、暗能量光谱仪器）调查提供了这些系统中单个恒星的位置、速度和化学丰度时，完整的（如矮星系、球状星团）和断裂的（如恒星流）银河系的同伴成为极其强大的探测器。通过分析这些数据集，我们将能够了解银河系恒星晕的组成部分，最小质量星系的形成和演化，银河系晕的质量和形状，并最终了解暗物质的微观性质（例如粒子质量，横截面等）。我的研究计划的长期目标是探索近场宇宙学中最重要的开放性问题。该提案将集中于以下两个研究重点。首先，我们将分析来自南方恒星流光谱调查的数据——这是我于2018年与大约40名成员发起的一项调查——对6D相空间的20多个恒星流进行系统研究；我们将利用这个独特的样本不仅来约束银河系暗物质晕的质量，还将探索银河系恒星晕的起源和形成。其次，我们将利用世界上最大的光学望远镜（如麦哲伦望远镜、甚大望远镜、凯克望远镜等）对银河系最不亮卫星系统（即超暗矮星系和外晕星团）的光谱数据进行分析；我们将确定这些系统的动态质量、轨道历史和化学特征，了解最小星系和最小星团的形成和演化差异，以及对暗物质性质施加最严格的限制。

The Milky Way's outer halo is one of the best places in the Universe to learn about the formation and evolution of galaxies and the nature of the dark matter. In particular, the intact (e.g. dwarf galaxies, globular clusters) and disrupted (e.g. stellar streams) companions of the Milky Way become extremely powerful probes when positions, velocities, chemical abundances of individual stars in these systems are provided by the recent space-based (e.g. Gaia) and ground-based (e.g. Dark Energy Survey, Dark Energy Spectroscopic Instrument) surveys. By analyzing these datasets, we will be able to understand the building blocks of the Milky Way's stellar halo, the formation and evolution of the least massive galaxies, the mass and shape of the Milky Way's halo, and ultimately, the microscopic properties of dark matter (e.g. particle mass, cross-section, etc.). The long-term goal of my research program is to explore the foremost open questions in near-field cosmology. This proposal will focus on the following two Research Thrusts. First, we will analyze the data from the Southern Stellar Stream Spectroscopic Survey -- a survey I initiated in 2018 with a group of ~40 members -- to pursue a systematic study of 20+ stellar streams in 6D phase space; we will use this unique sample to not only constrain the mass of the Milky Way's dark matter halo, but also probe the progenitors and formation of the Milky Way's stellar halo. Second, we will analyze the spectroscopic data on the least luminous satellite systems of the Milky Way (i.e. ultra-faint dwarf galaxies and outer halo star clusters) with world's largest optical telescopes (e.g. Magellan, Very Large Telescope, Keck, etc.); we will determine the dynamical mass, orbital history, and the chemical signatures of these systems, understanding the difference in the formation and evolution of the smallest galaxies and smallest star clusters, as well as putting the tightest constraints on dark matter properties.