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

Abstract

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 $0.25⩽E(J-K_s)⩽2.0$ mag and extinction $0.11⩽A_{Ks}⩽0.86$ mag for the sample clusters as expected in the bulge regions. The range of heliocentric distances is $6.8⩽D⩽11.4$ 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 $-1.40⩽$ [Fe/H] $⩽0.0$ dex and $t\approx 8-13$ Gyr respectively. The luminosities are calculated both in $K_s-$ and V-bands, recovering $-3.4⩽M_V⩽-7.5$. 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.

arXiv comment29 pages, 14 figures. Accepted for publication in A&A

References in corpus (55)

• Gaia Data Release 2. Summary of the contents and survey properties
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• VISTA Variables in the Via Lactea (VVV): The public ESO near-IR variability survey of the Milky Way
• A geometric distance measurement to the Galactic Center black hole with 0.3% uncertainty
• Extragalactic Globular Clusters and Galaxy Formation
• Global survey of star clusters in the Milky Way II. The catalogue of basic parameters
• Gaia EDR3 view on Galactic globular clusters
• The Optical to Mid-Infrared Extinction Law Based on the APOGEE, Gaia DR2, Pan-STARRS1, SDSS, APASS, 2MASS and WISE Surveys
• Mean proper motions, space orbits and velocity dispersion profiles of Galactic globular clusters derived from Gaia DR2 data
• Calibration of the Tip of the Red Giant Branch (TRGB)
• VVV DR1: The First Data Release of the Milky Way Bulge and Southern Plane from the Near-Infrared ESO Public Survey VISTA Variables in the Via Lactea
• The VISTA Science Archive
• A systematic survey for infrared star clusters with |b|<20deg using 2MASS
• The age of the oldest Open Clusters
• A new IR-Array photometric survey of Galactic Globular Clusters: A detailed study of the RGB sequence as a step towards the global testing of stellar models
• Near-IR properties of 24 Globular Clusters in the Galactic Bulge
• VIRAC: The VVV Infrared Astrometric Catalogue
• The VISTA ZYJHKs Photometric System: Calibration from 2MASS
• The First Detection of Blue Straggler Stars in the Milky Way Bulge
• Uncloaking globular clusters in the inner Galaxy
• The Red Giant Branch in the Near-Infrared Colour-Magnitude Diagrams. I: The calibration of photometric indices
• New galactic open cluster candidates from DSS and 2MASS imagery
• Gaia Data Release 1. Testing the parallaxes with local Cepheids and RR Lyrae stars
• Near Infrared properties of 12 Globular Clusters toward the inner Bulge of the Galaxy
• Empirical photometric calibration of the Gaia Red Clump: colours, effective temperature and absolute magnitude
• Discovery of VVV CL001. A Low-Mass Globular Cluster Next to UKS~1 in the Direction of the Galactic Bulge
• Milky Way demographics with the VVV survey. IV. PSF photometry from almost one billion stars in the Galactic bulge and adjacent southern disk
• New near-infrared period-luminosity-metallicity relations for RR Lyrae stars and the outlook for Gaia
• New galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge
• FSR 1716: A new Milky Way Globular Cluster confirmed using VVV RR Lyrae stars
• A Deep View of a Fossil Relic in the Galactic Bulge: The Globular Cluster HP1
• A new class of fossil fragments from the hierarchical assembly of the Galactic bulge
• Mapping the stellar age of the Milky Way bulge with the VVV. III. High resolution reddening map
• Ages of the Bulge globular clusters NGC 6522 and NGC 6626 (M28) from HST Proper-motion-cleaned Color-Magnitude Diagrams
• Analysis of the physical nature of 22 New VVV Survey Globular Cluster candidates in the Milky Way Bulge
• The ACS Survey of Galactic Globular Clusters XI: The Three-Dimensional Orientation of the Sagittarius Dwarf Spheroidal Galaxy and its Globular Clusters
• Properties of Star Clusters - I: Automatic Distance and Extinction Estimates
• Globular cluster candidates in the Galactic bulge: Gaia and VVV view of the latest discoveries
• Three candidate globular clusters discovered in the Galactic bulge
• High-resolution abundance analysis of four red giants in the globular cluster NGC 6558
• The enigmatic globular cluster UKS~1 obscured by the bulge: \textit{H}-band discovery of nitrogen-enhanced stars
• VVVX-Gaia Discovery of a Low Luminosity Globular Cluster in the Milky Way Disk
• Establishing the Galactic Centre Distance Using VVV Bulge RR Lyrae Variables
• Confirmation and physical characterization of the new bulge globular cluster Patchick 99 from the VVV and Gaia surveys
• Discovery of a new nearby globular cluster with extreme kinematics located in the extension of a halo stream
• AL 3 (BH 261): a new globular cluster in the Galaxy
• Dynamical Masses and Stellar Evolutionary Model Predictions of M-Stars
• Physical characterization of recently discovered globular clusters in the Sagittarius dwarf spheroidal galaxy II. Metallicities, ages and luminosities
• New variable stars discovered in the fields of three Galactic open clusters using the VVV Survey
• Near-IR period-luminosity relations for pulsating stars in $\omega$ Centauri (NGC 5139)
• SOAR BVI Photometry of the Metal-Poor Bulge Globular Cluster NGC 6642
• The RR Lyrae projected density distribution from the Galactic centre to the halo
• Constraining the Dust Opacity Law in Three Small and Isolated Molecular Clouds
• The Proper Motion of the Globular Cluster NGC 6553 and of Bulge Stars with HST

Cited by in corpus (3)

• A new low-luminosity globular cluster discovered in the Milky Way with the VVVX survey
• Gaia-IGRINS synergy: Orbits of Newly Identified Milky Way Star Clusters
• Variable stars in the VVV globular clusters. II. NGC6441, NGC6569, NGC6626 (M28), NGC6656 (M22), 2MASS-GC02, and Terzan10