NGC 5128 Globular Cluster Candidates Out to 150 kpc: A Comprehensive Catalog from Gaia and Ground-based Data*

Abstract

Abstract We present a new catalog of 40,502 globular cluster (GC) candidates in NGC 5128 out to a projected radius of ∼150 kpc based on data from the Panoramic Imaging Survey of Centaurus and Sculptor, the Gaia Data Release 2, and the NOAO Source Catalog. Ranking these candidates based on the likelihood that they are true GCs, we find that approximately 1900 belong to our top two ranking categories and should be the highest priority for spectroscopic follow-up for confirmation. Taking into account our new data and a vetting of previous GC catalogs, we estimate a total GC population of 1450 ± 160 GCs. We show that a substantial number of sources previously argued to be low-velocity GCs are instead foreground stars, reducing the inferred GC velocity dispersion. This work showcases the power of Gaia to identify slightly extended sources at the ∼4 Mpc distance of NGC 5128, enabling accurate identification of GCs throughout the entire extended halo, not just the inner regions that have been the focus of most previous work.