Obscured clusters. I. GLIMPSE 30 – A young Milky Way star cluster hosting Wolf-Rayet stars^*

¹ Departamento de Fisíca y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 644, Playa Ancha, Casilla 5030, Valparaíso, Chile e-mail: radostin.kurtev@uv.cl; jura.borissova@uv.cl
² Instituto de Astronomia, Universidad Nacional Autónoma de México, Apartado Postal 70-254, CD Universitaria, CP 04510, Mexico DF, Mexico e-mail: georgiev@astroscu.unam.mx
³ Universitá di Padova, Dipartimento di Astronomia, Vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: sergio.ortolani@unipd.it
⁴ European Southern Observatory, Ave. Alonso de Cordova 3107, Casilla 19, Santiago 19001, Chile e-mail: vivanov@eso.org

Received: 7 November 2006
Accepted: 17 August 2007

Abstract

Context.Young massive clusters are usually deeply embedded in dust and gas. They represent excellent astrophysical laboratories for the study of massive stars. Clusters with Wolf-Rayet (WR) stars are of special importance, since this enables us to study a coeval WR population at a uniform metallicity and known age.

Aims.We started a long-term project to search the inner Milky Way for hidden star clusters and to study them in detail. GLIMPSE 30 (G30) is one of these clusters. It is situated near the Galactic plane (, ) and we determine its physical parameters and investigate its high-mass stellar content especially WR stars.

Methods.Our analysis is based on SOFI/NTT imaging and low resolution () spectroscopy of the brightest cluster members in the K atmospheric window. For the age determination we applied isochrone fits for MS and Pre-MS stars. We derived stellar parameters of the WR stars candidates using a full nonLTE modeling of the observed spectra.

Results.Using a variety of techniques we found that G30 is very young cluster, with age t ≈ 4 Myr. The cluster is located in the Carina spiral arm, it is deeply embedded in dust and suffers reddening of  mag. The distance to the object is  kpc. The mass of the cluster members down to 2.35  is ~ 1600 . The cluster's MF for the mass range of 5.6 to 31.6  shows a slope of . The total mass of the cluster obtained by this MF down to 1  is about  . The spectral analysis and the models allow us to conclude that at least one Ofpe/WN and two WR stars can be found in G30. The WR stars are of the WN6-7 hydrogen rich type with progenitor masses of more than 60 .

Conclusions.G30 is a new member of the family of young Galactic clusters hosting WR stars. It is a factor of two to three less massive than some of the youngest super-massive star clusters like Arches, Quintuplet and the Central cluster and is their smaller analog.