Letter to the Editor

Discovery of new globular clusters in the Sagittarius dwarf galaxy

¹ Departamento de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, Fern’ındez Concha 700, Las Condes, Santiago, Chile
e-mail: vvvdante@gmail.com
² Vatican Observatory, Vatican City State 00120, Italy
³ INAF-Osservatorio Astronomico di Capodimonte, Salita Moiariello 16, 80131 Naples, Italy
⁴ Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copayapu 485, Copiapó, Chile
⁵ Institut Utinam, CNRS UMR 6213, Université Bourgogne-Franche-Comté, OSU THETA Franche-Comté, Observatoire de Besançon, BP 1615, 25010 Besançon Cedex, France
⁶ Centro de Investigación en Astronomía, Universidad Bernardo O’Higgins, Avenida Viel 1497, Santiago, Chile
⁷ Centro de Astronomía (CITEVA), Universidad de Antofagasta, Av. Angamos 601, Antofagasta, Chile
⁸ Millennium Institute of Astrophysics, Santiago, Chile
⁹ Institute of Astronomy, University of Cambridge, Madingley Rd, Cambridge CB3 0HA, UK
¹⁰ Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK
¹¹ Max-Planck for Astronomy, Koenigstuhl 17, 69117 Heidelberg, Germany
¹² European Southern Observatory, Karl-Schwarszchild-Str. 2, 85748 Garching b. Munich, Germany
¹³ Departamento de Fisica, Universidade Federal de Santa Catarina, Trindade 88040-900, Florianopolis, SC, Brazil
¹⁴ Observatorio Astronómico Universidad Nacional de Córdoba, Laprida 854, Córdoba 5000, Argentina
¹⁵ University of California – Davis, Davis, CA, USA
¹⁶ Department of Chemistry and Physics, Mount Saint Vincent University, Halifax, Nova Scotia B3M 2J6, Canada
¹⁷ Department of Astronomy and Physics, Saint Mary’s University, Halifax, Nova Scotia B3H 3C3, Canada

Received: 21 January 2021
Accepted: 21 February 2021

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.