Collaborative Research: Fingerprinting Stellar Halos- Tracing the Assembly of the Andromeda Galaxy with Detailed Chemical Abundances

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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 scientific 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.