Discovery of new globular clusters in the Sagittarius dwarf galaxy

D Minniti,J J Clariá,J B Pullen,J Alonso-García,R K Saito,V Ripepi,F Vivanco Cádiz,E R Garro,M Gómez,M Gregg,P W Lucas,D Majaess,J G Fernández-Trincado,M Hempel,T Palma,L C Smith,M Rejkuba

doi:10.1051/0004-6361/202140395

Abstract

Context. Globular clusters (GCs) are witnesses of the past accretion events onto the Milky Way. In particular, the GCs of the Sagittarius (Sgr) dwarf galaxy are important probes of an on-going merger. Aims. Our main goal is to search for new GC members of this dwarf galaxy using the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-infrared database combined with the Gaia Early Data Release 3 (EDR3) optical database. Methods. We investigated all VVVX-enabled discoveries of GC candidates in a region covering about 180 sq. deg. toward the bulge and the Sgr dwarf galaxy. We used multiband point-spread function photometry to obtain deep color-magnitude diagrams (CMDs) and luminosity functions (LFs) for all GC candidates, complemented by accurate Gaia-EDR3 proper motions (PMs) to select Sgr members and variability information to select RR Lyrae which are potential GC members. Results. After applying a strict PM cut to discard foreground bulge and disk stars, the CMDs and LFs for some of the GC candidates exhibit well defined red giant branches and red clump giant star peaks. We selected the best Sgr GCs, estimating their distances, reddenings, and associated RR Lyrae. Conclusions. We discover 12 new Sgr GC members, more than doubling the number of GCs known in this dwarf galaxy. In addition, there are 11 other GC candidates identified that are uncertain, awaiting better data for confirmation.

Highlights

Globular clusters (GCs) are important in astrophysics, and one of their latest outstanding applications is that they can be used to characterize possible ancient accretion events that contributed to build the Milky Way (MW) galaxy as we know it
Our main goal is to search for new GC members of this dwarf galaxy using the VISTA Variables in the Via Lactea Extended Survey (VVVX) near-infrared database combined with the Gaia Early Data Release 3 (EDR3) optical database
We have identified 23 candidate GCs that may belong to the Sgr dwarf galaxy from the VVV/VVVX surveys searches

Summary

Introduction

Globular clusters (GCs) are important in astrophysics, and one of their latest outstanding applications is that they can be used to characterize possible ancient accretion events that contributed to build the Milky Way (MW) galaxy as we know it By measuring their orbital and chemical properties, the GCs have been used to identify some of these past mergers, such as the Sagittarius (Sgr) dwarf galaxy, Gaia-EnceladusSausage, and Sequoia, to mention a few (e.g., Helmi et al 2018; Belokurov et al 2018; Massari et al 2019; Myeong et al 2019; Barba et al 2019; Vasiliev 2019; Huang & Koposov 2021). This was difficult because of the presence of heavy foreground contamination by disk and bulge field stars along the line of sight.

Data for the new Sgr GCs

Distances and other physical parameters

Conclusions