Inspection of 19 globular cluster candidates in the Galactic bulge with the VVV survey

• Published in: arXiv.org
• Main Authors: Garro, E R, Minniti, D, Gómez, M, Alonso-García, J, Ripepi, V, Fernández-Trincado, J G, F Vivanco Cádiz
• Format: Paper Journal Article
• Language: English
• Published: Ithaca Cornell University Library, arXiv.org 16.11.2021
• Subjects: Decontamination; Extinction; Galactic bulge; Galactic clusters; Globular clusters; Inspection; Kinematics; Luminosity; Mathematical analysis; Metallicity; Open clusters; Physics - Astrophysics of Galaxies; Workflow
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2111.08317

The census of the globular clusters (GCs) in the Milky Way (MW) is still a work in progress. We explore the nature of 19 new GC candidates in the Galactic bulge, based on the analysis of their colour-magnitude diagrams (CMDs) in the near-IR, using the VISTA Variables in the Via Láctea Survey (VVV) database. We estimate their main astrophysical parameters: reddening and extinction, distance, total luminosity, mean cluster proper motions (PMs), metallicity and age. We obtain the cluster catalogues including the likely cluster members by applying a decontamination procedure on the observed CMDs, based upon the vector PM diagrams from VIRAC2. We estimate a wide reddening range of the \(0.25 \leqslant E(J-K_s) \leqslant 2.0\) mag and extinction \(0.11 \leqslant A_{Ks} \leqslant 0.86\) mag for the sample clusters as expected in the bulge regions. The range of heliocentric distances is \(6.8\leqslant D\leqslant 11.4\) kpc. This allows us to place these clusters between 0.56 and 3.25 kpc from the Galactic centre, assuming \(R_{\odot}=8.2\) kpc. Also, their PMs are kinematically similar to the typical motion of the Galactic bulge, apart from VVV-CL160, which shows different PMs. We also derive their metallicities and ages, finding \(-1.40 \leqslant\) [Fe/H] \(\leqslant 0.0\) dex and \(t\approx 8-13\) Gyr respectively. The luminosities are calculated both in \(K_{s}-\) and V-bands, recovering \(-3.4 \leqslant M_V \leqslant -7.5\). We also examine the possible RR Lyrae members found in the cluster fields. Based on their positions, kinematics, metallicities and ages and comparing our results with the literature, we conclude that 9 candidates are real GCs, 7 need more observations to be fully confirmed as GCs, whereas 3 candidates are discarded for being younger open clusters.