VVVX survey dusts off a new intermediate-age star cluster in the Milky Way disk

TL;DR

This paper reports the discovery and detailed analysis of a new intermediate-age star cluster, Garro 03, in the Milky Way disk, using multi-band photometric data to determine its physical parameters and nature.

Contribution

It presents the first identification and characterization of Garro 03, a distant, low-luminosity, metal-rich star cluster, expanding the census of Galactic clusters and providing insights into their properties.

Findings

Garro 03 is located at 14.1 kpc from the Sun and 10.6 kpc from the Galactic center.

It has an age of approximately 3 Gyr and metallicity [Fe/H] ≈ -0.5.

The cluster is a distant, low-luminosity, metal-rich intermediate-age star cluster.

Abstract

Our primary long-term objective is to seek out additional star clusters in the poorly studied regions of the MW. The aim of this pursuit is to finalize the MG's globular and open cluster system census and to gain a comprehensive understanding of both the formation and evolution of these systems and our Galaxy as a whole. We report the discovery of a new star cluster, named Garro~03. We investigated this target using a combination of near-infrared and optical databases. We employed VVVX and 2MASS data in the NIR, and Gaia DR3 and the DECaPS2 datasets in the optical passband. We performed a photometrical analysis in order to derive its main physical parameters. Garro~03 is located at equatorial coordinates RA=14:01:29.3 and Dec=-65:30:57.0. It is not heavily affected by extinction $A_{Ks}=0.25\pm 0.04$ mag. It is located at heliocentric distance of $14.1\pm0.5$ kpc, which places Garro~03 at 10.6 kpc from the Galactic centre and Z=-0.89 kpc below the Galactic plane. We calculated the mean cluster PM of ($\mu_{\alpha}^{\ast},\mu_{\delta}) = (-4.57\pm 0.29,\ -1.36\pm 0.27$) mas yr$^{-1}$. We derived an age=3 Gyr and [Fe/H]~$= -0.5\pm 0.2$ by the isochrone-fitting method. The total luminosity was derived in the $K_s$ and V-bands, finding $M_{Ks} = -6.32\pm 1.10$ mag and $M_V =-4.06$ mag. The core and tidal radii were measured constructing the Garro~03 radial density profile and fitting the King model, obtaining $r_c = 3.07\pm 0.98$ pc and $r_t = 19.36\pm 15.96$ pc. We photometrically confirm the cluster nature for Garro~03, located in the Galactic disk. It is a distant, low-luminosity, metal-rich star cluster of intermediate age. We also searched for possible signatures (streams or bridges) between Garro~03 and Garro~01, but we exclude a possible companionship. We need spectroscopic data to classify it as an old open cluster or a young globular cluster, and to understand its origin.