NGC 5128 globular cluster candidates out to 150 kpc: a comprehensive catalog from Gaia and ground based data

TL;DR

This paper presents a comprehensive catalog of over 40,000 globular cluster candidates in NGC 5128 using Gaia and ground-based data, refining the total population estimate and demonstrating Gaia's effectiveness in identifying GCs at large distances.

Contribution

The study provides the largest catalog of GC candidates in NGC 5128, combining multiple data sources and introducing a ranking system for follow-up prioritization, improving upon previous catalogs.

Findings

Estimated total GC population of 1450 ± 160.

Identified ~1900 high-priority candidates for spectroscopic confirmation.

Reduced previous GC counts by correcting for foreground star contamination.

Abstract

We present a new catalog of 40502 globular cluster (GC) candidates in NGC 5128 out to a projected radius of $\sim$150 kpc, based on data from the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), 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 $1450 \pm 160$ 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 $\sim 4$ 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.