Discovery of VVV CL001

A low-mass globular cluster next to UKS 1 in the direction of the Galactic bulge

¹ Departamento de Astronomía y AstrofísicaP. Universidad Católica de Chile, Casilla 306, Santiago, Chile
e-mail: dante@astro.puc.cl; mhempel@astro.puc.cl; itoledoc@astro.puc.cl; jalonso;@astro.puc.cl; r.saito@astro.puc.cl; mcatelan@astro.puc.cl; ajordan@astro.puc.cl; mzoccali@astro.puc.cl
² European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago de Chile 19, Chile
e-mail: vivanov@eso.org; gcarraro@eso.org
³ Departamento de Astronomía, Universidad de Concepción, Bio-Bio 160-C, Chile
e-mail: dgeisler@astro-udec.cl; cmbidin@astro-udec.cl
⁴ Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Valparaíso, Chile
e-mail: jura.borissova@uv.cl; radostin.kurtev@uv.cl
⁵ Inst Astronomico e Geofisico-Depto Astronomia, Universidade de São Paulo, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil
e-mail: barbuy@astro.iag.usp.br
⁶ Observatorio Astronomico, Laprida 854, Córdoba 5000, Argentina
e-mail: jjclaria@gmail.com
⁷ European Southern Observatory, Karl-Schwarszchild Strasse 2, 85748 Garching/ bei München, Germany
e-mail: mrejkuba@eso.org
⁸ Astronomy Unit, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London, E1 4NS, UK,
e-mail: j.p.emerson@qmul.ac.uk

Received: 20 September 2010
Accepted: 28 November 2010

Abstract

Context. It is not known how many globular clusters may remain 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 search for new ones, hidden in regions of large extinction.

Methods. From deep near-infrared images, we derive deep JHK_S-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 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. On the basis of near-infrared colour − magnitude diagrams, we also find that VVV CL001 has E(B − V) ~ 2.0, and that it is at least as metal-poor as UKS 1, although its distance remains uncertain.

Conclusions. Our finding confirms the previous projection that the central region of the Milky Way harbours 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.