Selecting Potential Extra-Tidal Stars from Globular Clusters as Targets for Spectroscopy
Faculty Mentor Information
Dr. Katie Devine, College of Idaho; and Dr. Andrea Kunder, Saint Martin's University
Presentation Date
7-16-2026
Abstract
Globular clusters are gravitationally bound groups of thousands to millions of stars that contain some of the oldest stars in the galaxy. We hypothesize that a significant number of stars in the center of the Milky Way, or “the bulge,” originally formed in globular clusters and were captured by gravity as the clusters orbited close to the bulge. Identifying stars that have been stripped off clusters tells us how clusters contribute stars to the bulge. To confirm that a star was part of a cluster, we look at its chemical and kinematic properties and see if the properties align with those of the cluster. We use spectroscopy to find the metallicities and radial velocities (RV) of candidate stripped stars. To determine likely candidates, we fit an isochrone to high confidence cluster members, which tells us the age of the cluster. We used this isochrone to select additional possible cluster members at a greater, extra-tidal distance. We identified ~500 candidates whose spectra we will observe with the Anglo-Australian Telescope. These spectra will provide the metallicities and RVs of the stars which will help us determine if the stars originated in the cluster.
Selecting Potential Extra-Tidal Stars from Globular Clusters as Targets for Spectroscopy
Globular clusters are gravitationally bound groups of thousands to millions of stars that contain some of the oldest stars in the galaxy. We hypothesize that a significant number of stars in the center of the Milky Way, or “the bulge,” originally formed in globular clusters and were captured by gravity as the clusters orbited close to the bulge. Identifying stars that have been stripped off clusters tells us how clusters contribute stars to the bulge. To confirm that a star was part of a cluster, we look at its chemical and kinematic properties and see if the properties align with those of the cluster. We use spectroscopy to find the metallicities and radial velocities (RV) of candidate stripped stars. To determine likely candidates, we fit an isochrone to high confidence cluster members, which tells us the age of the cluster. We used this isochrone to select additional possible cluster members at a greater, extra-tidal distance. We identified ~500 candidates whose spectra we will observe with the Anglo-Australian Telescope. These spectra will provide the metallicities and RVs of the stars which will help us determine if the stars originated in the cluster.