2023 113 P

High-Resolution Integrated Light Spectroscopy of M31 GCs B006 and B403

By: Allison Swart

Department: Physics & Astronomy

Faculty Advisor: Dr. Charli Sakari

The chemical signature of astronomical objects such as globular clusters (GCs) is a powerful tool for studying their formation history. Elements form via a variety of methods, so comparing the relative abundances of different categories of elements in a GC can describe the types of processes that were most important to its assembly. Comparing the abundances for a singular GC with other objects in the galaxy can, in turn, reveal the composition and formation history of the galaxy as a whole. Analysis of this type has been performed for GCs in the Milky Way, but the process is more difficult for extragalactic GCs due to an inability to resolve individual stars. Extragalactic GCs must be studied by integrated light (IL) spectroscopy, using chemical abundances of the GC as a whole to examine its place in the rest of the galaxy. In this work, we present optical elemental abundances of the clusters B006 and B403 in the Andromeda galaxy (M31) by high-resolution IL analysis of data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE). The cluster B006 is a standard GC, allowing for the calibration of IL techniques, while B407 is a valuable target due to its possible association with the Giant Stellar Stream (GSS). Using synthesized abundance models, we determine relative abundances for the CNO, light, and α-element types for each of the GCs. For the cluster B006, we compare these abundances with previous high-resolution IL observations by Sakari et al. 2016. For the cluster B403, we determine new abundances that offer important constraints on its birth site and possible association with the GSS. Together, these two clusters shed light on the complex assembly history of M31.