@article{83371e5ff6584375bd255e8b047b8f14,
title = "Massive open star clusters using the VVV survey: II. Discovery of six clusters with Wolf-Rayet stars",
abstract = "Context. The ESO Public Survey {"}VISTA Variables in the V{\'i}a L{\'a}ctea{"} (VVV) provides deep multi-epoch infrared observations for an unprecedented 562 sq. degrees of the Galactic bulge, and adjacent regions of the disk. Nearly 150 new open clusters and cluster candidates have been discovered in this survey. Aims. This is the second in a series of papers about young, massive open clusters observed using the VVV survey. We present the first study of six recently discovered clusters. These clusters contain at least one newly discovered Wolf-Rayet (WR) star. Methods. Following the methodology presented in the first paper of the series, wide-field, deep JHKs VVV observations, combined with new infrared spectroscopy, are employed to constrain fundamental parameters for a subset of clusters. Results. We find that the six studied stellar groups are real young (2-7 Myr) and massive (between 0.8 and 2.2 × 103 M{\texttrademark}) clusters. They are highly obscured (AV ∼ 5-24 mag) and compact (1-2 pc). In addition to WR stars, two of the six clusters also contain at least one red supergiant star, and one of these two clusters also contains a blue supergiant. We claim the discovery of 8 new WR stars, and 3 stars showing WR-like emission lines which could be classified WR or OIf. Preliminary analysis provides initial masses of ∼30-50 M{\texttrademark} for the WR stars. Finally, we discuss the spiral structure of the Galaxy using the six new clusters as tracers, together with the previously studied VVV clusters.",
keywords = "Infrared: stars, Open clusters and associations: general, Stars: Wolf-Rayet, Stars: massive, Surveys",
author = "Chen{\'e}, {A. N.} and J. Borissova and C. Bonatto and Majaess, {D. J.} and G. Baume and Clarke, {J. R.A.} and R. Kurtev and O. Schnurr and Bouret, {J. C.} and M. Catelan and Emerson, {J. P.} and C. Feinstein and D. Geisler and {De Grijs}, R. and A. Herv{\'e} and Ivanov, {V. D.} and Kumar, {M. S.N.} and P. Lucas and L. Mahy and F. Martins and F. Mauro and D. Minniti and {Moni Bidin}, C.",
note = "Funding Information: We would like to warmly thank Ignacio Toledo, Roberto Gamen and the VVV science team for the helping to improve the images in Fig. 1. We also thank the anonymous referee for his help in improving this work. This project is supported by the Chilean Ministry for the Economy, Development, and Tourism{\textquoteright}s Programa Iniciativa Cient{\'i}fica Milenio through grant P07-021-F, awarded to The Milky Way Millennium Nucleus. A.N.C., D.G. and D.M. gratefully acknowledge support from the Chilean Centro de Astrof{\'i}sica FONDAP No. 15010003 and the BASAL Chilean Centro de Excelencia en Astrof{\'i}sica y Tecnolog{\'i}as Afines (CATA) PFB-06. A.N.C. also acknowledges the Comite Mixto ESO-Gobierno de Chile. J.B. is supported by FONDECYT No. 1120601 and R.K. by the Centro de Astrof{\'i}sica de Valpara{\'i}so and Proyecto DIUV23/2009. Support for M.C. is also provided by Proyecto Fondecyt Regular #1110326, and Anillo ACT-86. R.d.G. acknowledges partial research support through grant 11073001 from the National Natural Science Foundation of China. MSNK is supported by a Ci{\^e}ncia 2007 contract, funded by FCT/MCTES (Portugal) and POPH/FSE (EC). The data used in this paper have been obtained with NTT/SofI at ESO{\textquoteright}s La Silla Observatory, and with Clay/MMIRS at Las Campanas Observatory. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. We gratefully acknowledge use of data from the ESO Public Survey programme ID 179.B-2002 taken with the VISTA telescope, and data products from the Cambridge Astronomical Survey Unit.",
year = "2013",
doi = "10.1051/0004-6361/201220107",
language = "English",
volume = "549",
journal = "Astronomy and Astrophysics",
issn = "0004-6361",
publisher = "EDP Sciences",
}