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

星系最外层的恒星保存了恒星诞生的化石记录和该星系在其一生中的动力学。这些恒星晕远远超出了银河系拥挤的内部区域，在那里，大多数恒星居住在圆盘或致密球体中。恒星晕被认为是由在星系新形成的盘中很早就形成的恒星，以及原本属于落入大星系并被撕裂的较小矮小星系的恒星组成的。研究人员将研究仙女座星系恒星晕中恒星的物理性质，并确定这两种不同方式对星系晕贡献恒星的相对重要性。他们的目标是了解大质量星系是如何增长的。他们将推断被摧毁的“矮小”星系的性质以及它们形成新星的速度。这将让我们深入了解直到今天才存活下来的矮小星系的性质。该项目将培训年轻的天文学家，并向高中生介绍天文研究。仙女座星系是距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，它与更多的小星系合并而不是银河系。研究人员和学生们将使用凯克望远镜以前对数万颗恒星进行观测的光谱档案，还将进行新的光谱观测。他们将使用这些光谱来测量原子元素的丰度，并追踪恒星形成的化学环境的性质。研究人员将对仙女座菌株的恒星晕进行首次大规模的化学丰度研究。研究人员将招募学生从事与这一计划相关的夏季研究。他们将把招聘重点放在有很大一部分学生来自科学、技术、工程和数学(STEM)代表性不足的人口群体的学校。完成一个尖端的天文研究项目将使这些学生了解STEM领域的工作，并让他们有信心在STEM职业生涯中取得成功。

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.