COLLABORATIVE RESEARCH: Fingerprinting Stellar Halos - Tracing the Assembly of the Andromeda Galaxy with Detailed Chemical Abundances

星系最外层区域的恒星保存了恒星诞生的化石记录和星系一生的动态。这些恒星晕远远超出了星系拥挤的内部区域，在那里，大多数恒星驻留在圆盘或密集的球体中。恒星晕被认为是由早期形成的恒星组成的，在星系新形成的圆盘上，以及最初是较小的矮星系的一部分的恒星，这些恒星落入大星系并被撕裂。研究人员将研究仙女座星系恒星晕中恒星的物理特性，并将确定这两种不同方式对星系晕的贡献的相对重要性。他们的目标是了解大质量星系是如何成长的。他们将推断出被摧毁的“矮”星系的性质以及它们形成新恒星的速度。这将使我们深入了解矮星系的特性，这些矮星系直到今天才存在。该项目将培养年轻的天文学家，并向高中生介绍天文研究。仙女座星系是离我们最近的大星系。它在许多方面与我们的银河系相似，但有证据表明它合并了比银河系更多的小星系。研究人员和学生们将使用凯克望远镜的光谱档案，这些光谱档案来自于之前对数万颗恒星的观测，他们还将进行新的光谱观测。他们将利用这些光谱来测量原子元素的丰度，并追踪恒星形成时的化学环境的特性。研究人员将对仙女座的恒星光晕进行首次大规模的化学丰度研究。研究人员将招募学生参与与该项目相关的暑期研究。他们将把招聘重点放在那些在科学、技术、工程和数学（STEM）领域代表性不足的人口群体中有很大一部分学生的学校。完成一个前沿的天文学研究项目，既可以让这些学生进入STEM领域工作，也可以让他们有信心在STEM领域取得成功。

The stars in the outermost regions of galaxies preserve a fossil record of the birth of stars and dynamics of that galaxy over its lifetime. These stellar halos extend far beyond the crowded inner regions of galaxies, where the majority of the stars reside in disks or dense spheres. Stellar halos are thought to be made of stars that formed very early on, in the galaxy's newly formed disk, as well as stars that were originally part of smaller, dwarf, galaxies that fell into the large galaxy and were torn apart. The investigators will study the physical properties of the stars in the Andromeda galaxy's stellar halo, and will determine the relative importance of these two different ways of contributing stars to a galaxy's halo. Their goal is understanding of how massive galaxies grow. They will deduce the properties of destroyed "dwarf" galaxies and their rate of forming new stars. This will give insight into the properties of dwarf galaxies that did not survive until the present day. This program will train young astronomers and introduce high school students to astronomical research.The Andromeda galaxy is the nearest large galaxy to our own. It is similar in many ways to our Milky Way galaxy, but shows evidence that it has merged with more small galaxies than the Milky Way. The investigators, along with students, will use an archive of Keck telescope spectra from previous observations of tens of thousands of stars, and will also perform new spectroscopic observations. They will use the spectra to measure the abundances of atomic elements and track the properties of the chemical environment in which the stars formed. The investigators will perform the first large-scale chemical abundance study of Andromeda's stellar halo.The investigators will recruit students to engage in summer research related to this program. They will focus their recruitment at schools that have a large fraction of students from demographic groups that are under-represented in science, technology, engineering, and mathematics (STEM). Completing a cutting-edge astronomical research project will both introduce these students to working in a STEM field and give them confidence that they can succeed in a STEM career.