Applying Chemical Evolution Models to Andromeda’s Stellar Halo and Tidal Debris

Galaxies form in part from the accretion of stars and gas. As external galaxies accrete into Milky Way like galaxies, they form a stellar halo and tidal debris around the host galaxy. Studying the chemical abundances in a galaxy’s stellar halo can give insight on how the galaxy formed over cosmic time. The Andromeda Galaxy is the closest galaxy similar to the Milky Way. Modeling the chemical evolution of Andromeda’s stellar halo is a stepping stone to learning about the history of the broader universe, since this type of modeling will be the first beyond the Milky Way system. The Elemental Abundances in M31 survey has measured [Fe/H] and [alpha/Fe] for hundreds of individual red giant branch stars from Keck/DEIMOS spectra in M31. We have produced Chempy chemical evolution models in order to compare them to the chemical abundances of the stellar halo and tidal debris components in this data set. By varying the assumptions of these models and plotting the best fit chemical evolution track against the M31 data, we aim to obtain new information on the history of stars and gas that formed Andromeda.