Eight more low luminosity globular clusters in the Sagittarius dwarf galaxy

TL;DR

This study identifies eight new low-luminosity, metal-rich globular clusters in the Sagittarius dwarf galaxy using combined infrared and optical data, enhancing understanding of its cluster system amid foreground contamination.

Contribution

The paper presents the discovery of eight new globular clusters in the Sagittarius dwarf galaxy through a tailored proper motion and color-magnitude analysis, expanding the known cluster system.

Findings

Discovered 8 new globular clusters in the Sagittarius dwarf galaxy.

Most new GCs are metal-rich and low luminosity.

Total GCs in Sgr dwarf galaxy now 29.

Abstract

Context. The Sagittarius (Sgr) dwarf galaxy is merging with the Milky Way, and the study of its globular clusters (GCs) is important to understand the history and outcome of this ongoing process. Aims. Our main goal is to characterize the GC system of the Sgr dwarf galaxy. This task is hampered by high foreground stellar contamination, mostly from the Galactic bulge. Methods. We performed a GC search specifically tailored to find new GC members within the main body of this dwarf galaxy using the combined data of the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-infrared survey and the Gaia Early Data Release 3 (EDR3) optical database. Results. We applied proper motion (PM) cuts to discard foreground bulge and disk stars, and we found a number of GC candidates in the main body of the Sgr dwarf galaxy. We selected the best GCs as those objects that have significant overdensities above the stellar background of the Sgr galaxy and that possess color-magnitude diagrams (CMDs) with well-defined red giant branches (RGBs) consistent with the distance and reddening of this galaxy. Conclusions. We discover eight new GC members of the Sgr galaxy, which adds up to 29 total GCs known in this dwarf galaxy. This total number of GCs shows that the Sgr dwarf galaxy hosts a rather rich GC system. Most of the new GCs appear to be predominantly metal-rich and have low luminosity. In addition, we identify ten other GC candidates that are more uncertain and need more data for proper confirmation.