An Intriguing Globular Cluster in the Galactic Bulge from the VVV Survey

Abstract

Recent near-IR Surveys have discovered a number of new bulge globular cluster (GC) candidates that need to be further investigated. Our main objective is to use public data from the Gaia Mission, VVV, 2MASS and WISE in order to measure the physical parameters of Minni48, a new candidate GC located in the inner bulge of the Galaxy at l=359.35 deg, b=2.79 deg. Even though there is a bright foreground star contaminating the field, the cluster appears quite bright in near- and mid-IR images. We obtain deep decontaminated optical and near-IR colour-magnitude diagrams (CMDs) for this cluster. The heliocentric cluster distance is determined from the red clump (RC) and the red giant branch (RGB) tip magnitudes in the near-IR CMD, while the cluster metallicity is estimated from the RGB slope and the fit to theoretical isochrones. The GC size is found to be r = 6' +/- 1', while reddening and extinction values are E(J-Ks)=0.60 +/- 0.05 mag, A_G=3.23 +/- 0.10 mag, A_Ks=0.45 +/- 0.05 mag. The resulting mean Gaia proper motions are PMRA=-3.5 +/- 0.5 mas/yr, PMDEC=-6.0 +/- 0.5 mas/yr. The IR magnitude of the RC yields an accurate distance modulus estimate of (m-M)_0=14.61 mag, equivalent to a distance D=8.4 +/- 1.0 kpc. This is consistent with the optical distance estimate: (m-M)_0=14.67 mag, D=8.6 +/- 1.0 kpc, and with the RGB tip distance: (m-M)_0=14.45 mag, D=7.8 +/- 1.0 kpc. The derived metallicity is [Fe/H]=-0.20 +/- 0.30 dex. A good fit to the PARSEC stellar isochrones is obtained in all CMDs using Age = 10 +/- 2 Gyr. The total absolute magnitude of this GC is estimated to be M_Ks= -9.04 +/- 0.66 mag. Based on its position, kinematics, metallicity and age, we conclude that Minni48 is a genuine GC, similar to other well known metal-rich bulge GCs. It is located at a projected Galactocentric angular distance of 2.9 deg, equivalent to 0.4 kpc, being one of the closest GCs to the Galactic centre.

12 pages, 15 figures. Abridged abstract. Accepted for publication in the Astronomy & Astrophysics

References in corpus (18)

• Gaia Data Release 1: Catalogue validation
• Near-IR properties of 24 Globular Clusters in the Galactic Bulge
• The VISTA ZYJHKs Photometric System: Calibration from 2MASS
• Open clusters in dense fields: the importance of field-star decontamination for NGC5715, Lynga4, Lynga9, Trumpler23, Trumpler26 and Czernik37
• The brightness of the Red Giant Branch tip: Theoretical framework, a set of reference models, and predicted observables
• A Sequoia in the Garden: FSR 1758 - Dwarf Galaxy or Giant Globular Cluster?
• Extinction ratios in the inner Galaxy as revealed by the VVV survey
• Empirical photometric calibration of the Gaia Red Clump: colours, effective temperature and absolute magnitude
• Near-Infrared Photometry of Globular Clusters Towards the Galactic Bulge: Observations and Photometric Metallicity Indicators
• New galactic star clusters discovered in the VVV survey. Candidates projected on the inner disk and bulge
• Variable stars in the VVV globular clusters. I. 2MASS-GC02 and Terzan10
• Analysis of the physical nature of 22 New VVV Survey Globular Cluster candidates in the Milky Way Bulge
• Constraining Dust Extinction Properties via the VVV Survey
• CAPOS: The bulge Cluster APOgee Survey I. Overview and initial ASPCAP results
• Three candidate globular clusters discovered in the Galactic bulge
• Discovery of a new nearby globular cluster with extreme kinematics located in the extension of a halo stream
• New Galactic embedded clusters and candidates from a WISE Survey
• The RR Lyrae projected density distribution from the Galactic centre to the halo

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