Obscured clusters

IV. The most massive stars in [DBS2003] 179^⋆

¹ Departamento de Fisíca y AstronomíaFacultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, 5030 Casilla, Valparaíso, Chile
e-mail: jura.borissova@uv.cl; radostin.kurtev@uv.cl
² The Milky Way Millennium Nucleus, Av. Vicuña Mackenna 4860, 782-0436 Macul, Santiago, Chile
³ Instituto de Astronomia, Universidad Nacional Autónoma de México, Apartado Postal 70-254, CD Universitaria, CP 04510 Mexico DF, Mexico
e-mail: georgiev@astro.unam.mx
⁴ Department of Physics, University of Cincinnati, Cincinnati, OH 45221-0011, USA
e-mail: margaret.hanson@uc.edu
⁵ European Southern Observatory, Ave. Alonso de Cordova 3107, Casilla 19, 19001 Santiago, Chile
e-mail: vivanov@eso.org
⁶ Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
e-mail: Hillier@pitt.edu
⁷ Escuela Superios de Fisica y Matematicas, Instituto Politecnico Nacional, Mexico
e-mail: jzsargo@esfm.ipn.mx

Received: 27 October 2011
Accepted: 29 August 2012

Abstract

Aims. We report new results for the massive evolved and main sequence members of the young galactic cluster DBS2003 179. We determine the physical parameters and investigate the high-mass stellar content of the cluster, as well as of its close vicinity.

Methods. Our analysis is based on ISAAC/VLT moderate-resolution (R ≈ 4000) infrared spectroscopy of the brightest cluster members. We derive stellar parameters for sixteen of the stellar members, using full non-local thermodynamic equilibrium modeling of the obtained spectra.

Results. The cluster contains three late WN or WR/LBV stars (Obj 4, Obj 15, and Obj 20:MDM 32) and at least five OIf and five OV stars. According to the Hertzsprung-Russell diagram for DBS2003 179, the WR stars show masses above 85 ℳ_⊙, the OIf stars are between 40 and 80 ℳ_⊙, and the main sequence O stars are  >20 ℳ_⊙. There are indications of binarity for Obj 4 and Obj 11, and Obj 3 shows a variable spectrum. The cluster is surrounded by a continuous protostar formation region most probably triggered by DBS2003 179.

Conclusions. We confirm that DBS2003 179 is young massive cluster (2.5 × 10⁴ ℳ_⊙) very close to the Galactic center at the distance of 7.9 ± 0.8 kpc.