Discovery of VVV CL001. A Low-Mass Globular Cluster Next to UKS~1 in the Direction of the Galactic Bulge

TL;DR

This paper reports the discovery of a new low-mass globular cluster, VVV CL001, near UKS 1 in the Galactic bulge, using deep infrared imaging from the VVV survey, suggesting the Milky Way may host more hidden clusters.

Contribution

The study introduces the identification of VVV CL001 as a new globular cluster candidate in the Milky Way's bulge region, utilizing near-infrared photometry to detect previously unseen clusters.

Findings

VVV CL001 is at least as metal-poor as UKS 1.

Distance to VVV CL001 remains uncertain.

The discovery supports the idea of more hidden clusters in the Galactic bulge.

Abstract

Context: It is not known how many globular clusters may have been left undetected towards the Galactic bulge. Aims: One of the aims of the VISTA Variables in the Via Lactea (VVV) Survey is to accurately measure the physical parameters of the known globular clusters in the inner regions of the Milky Way and to search for new ones, hidden in regions of large extinction. Methods: Deep near infrared images give deep JHKs-band photometry of a region surrounding the known globular cluster UKS 1 and reveal a new low-mass globular cluster candidate that we name VVV CL001. Results: We use the horizontal branch red clump in order to measure E(B-V)~2.2 mag, $(m-M)_0$=16.01 mag, and D=15.9 kpc for the globular cluster UKS 1. Based on the near-infrared colour magnitude diagrams, we also measure that VVV CL001 has E(B-V)~2.0, and that it is at least as metal-poor as UKS 1, however, its distance remains uncertain. Conclusions: Our finding confirms the previous projection that the central region of the Milky Way harbors more globular clusters. VVV CL001 and UKS 1 are good candidates for a physical cluster binary, but follow-up observations are needed to decide if they are located at the same distance and have similar radial velocities.