New Galactic star clusters discovered in the VVV survey^{⋆,⋆⋆,⋆⋆⋆}

¹ Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030, Valparaíso, Chile
e-mail: jura.borissova@uv.cl; radostin.kurtev@uv.cl; j.clarke@dfa.uv.cl; paco.stilla@gmail.com; s.folkes@dfa.uv.cl; paco.stilla@gmail.com; s.sale@dfa.uv.cl; paco.stilla@gmail.com
² Universidade Federal do Rio Grande do Sul, Departamento de Astronomia CP 15051, RS, Porto Alegre 91501-970, Brazil
e-mail: charles@if.ufrgs.br; bica@if.ufrgs.br
³ Département de Physique and Observatoire du Mont Mégantic, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada
e-mail: artigau@ASTRO.UMontreal.CA
⁴ Facultad de Ciencias Astronómicas y Geofísicas, Instituto de Astrofísica de La Plata, Paseo del Bosque s/n, La Plata, Argentina
e-mail: gbaume@gmail.com
⁵ Departamento de Astronomía y Astrofísica, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, Casilla 306, Santiago 22, Chile
e-mail: dante@astro.puc.cl; itoledoc@gmail.com; mcatean@astro.puc.cl; itoledoc@gmail.com; mhempel@astro.puc.cl; itoledoc@gmail.com; rsaito@astro.puc.cl; itoledoc@gmail.com; jalonso@astro.puc.cl; itoledoc@gmail.com;
⁶ Departamento de Astronomía, Casilla 160, Universidad de Concepción, Chile
e-mail: achene@udec.cl; dgeisler@astro-udec.cl
⁷ Departamento de Astronomia, Universidade de Sao Paulo, Rua do Matao, 1226 – Cidade Universitaria, 05508-900 – Sao Paulo/SP  – Brasil
e-mail: bdias@astro.iag.usp.br
⁸ Centre for Astrophysics & Planetary Science, The University of Kent, Canterbury, Kent, CT2 7NH, UK
e-mail: df@star.kent.ac.uk
⁹ Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian District, Beijing 100871, PR China
e-mail: grijs@pku.edu.cn
¹⁰ Department of Astronomy and Space Science, Kyung Hee University, Yongin-shi, Kyungki-do 449-701, Republic of Korea
¹¹ European Southern Observatory, Ave. Alonso de Cordova 3107, Casilla 19, Santiago 19001, Chile
e-mail: vivanov@eso.org
¹² Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
e-mail: nanda@astro.up.pt
¹³ Centre for Astrophysics Research, University of Hertfordshire, Hatfield AL10 9AB, UK
e-mail: phyqpwl@herts.ac.uk
¹⁴ National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan
e-mail: motohide.tamura@nao.ac.jp
¹⁵ European Southern Observatory, Karl-Schawarzschild-Strasse 2, 85748 Garching bei Munchen, Germany
e-mail: mrejkuba@eso.org
¹⁶ Departamento de Física, Universidad de La Serena, Cisternas 1200 Norte, La Serena, Chile ; Instituto de Ciencias Astronómicas, de la Tierra y del Espacio (ICATE-CONICET), Av. España Sur 1512, J5402DSP, San Juan, Argentina
e-mail: rbarba@dfuls.cl
¹⁷ Department of Physics, University of Cincinnati, Cincinnati, OH 45221-0011, USA
e-mail: margaret.hanson@uc.edu
¹⁸ Vatican Observatory, V00120 Vatican City State, Italy

Received: 6 February 2011
Accepted: 3 June 2011

Abstract

Context. VISTA Variables in the Vía Láctea (VVV) is one of the six ESO Public Surveys operating on the new 4-m Visible and Infrared Survey Telescope for Astronomy (VISTA). VVV is scanning the Milky Way bulge and an adjacent section of the disk, where star formation activity is high. One of the principal goals of the VVV Survey is to find new star clusters of differentages.

Aims. In order to trace the early epochs of star cluster formation we concentrated our search in the directions to those of known star formation regions, masers, radio, and infrared sources.

Methods. The disk area covered by VVV was visually inspected using the pipeline processed and calibrated K_S-band tile images for stellar overdensities. Subsequently, we examined the composite JHK_S and ZJK_S color images of each candidate. PSF photometry of 15 × 15 arcmin fields centered on the candidates was then performed on the Cambridge Astronomy Survey Unit reduced images. After statistical field-star decontamination, color–magnitude and color–color diagrams were constructed and analyzed.

Results. We report the discovery of 96 new infrared open clusters and stellar groups. Most of the new cluster candidates are faint and compact (with small angular sizes), highly reddened, and younger than 5 Myr. For relatively well populated cluster candidates we derived their fundamental parameters such as reddening, distance, and age by fitting the solar-metallicity Padova isochrones to the color–magnitude diagrams.