Massive open star clusters using the VVV survey III. A young massive cluster at the far edge of the Galactic bar

Context. Young massive clusters are key to map the Milky Way’s structure, and near-infrared large area sky surveys have contributed strongly to the discovery of new obscured massive stellar clusters. Aims. We present the third article in a series of papers focused on young and massive clusters discovered in the VVV survey. This article is dedicated to the physical characterization of VVV CL086, using part of its OB-stellar population. Methods. We physically characterized the cluster using JHKS near-infrared photometry from ESO public survey VVV images, using the VVV-SkZ pipeline, and near-infrared K-band spectroscopy, following the methodology presented in the first article of the series. Results. Individual distances for two observed stars indicate that the cluster is located at the far edge of the Galactic bar. These stars, which are probable cluster members from the statistically field-star decontaminated CMD, have spectral types between O9 and B0 V. According to our analysis, this young cluster (1.0 Myr < age < 5.0 Myr) is located at a distance of 11+5-6 kpc, and we estimate a lower limit for the cluster total mass of (2.8+1.6-1.4) · 103 M⊙. It is likely that the cluster contains even earlier and more massive stars.

S.R.A. and A.N.C. were supported by the GEMINI-CONICYT project number 32110005. S.R.A. was also supported by the FONDECYT project No. 3140605. The VVV Survey is supported by ESO, by BASAL Center for Astrophysics and Associated Technologies PFB-06, by FONDAP Center for Astrophysics 15010003, and by the Ministry for the Economy, Development, and Tourism’s Programa Inicativa Científica Milenio through grant IC12009, awarded to The Millennium Institute of Astrophysics (MAS). Support for J.B. is provided by FONDECYT Regular No. 1120601, P.A. acknowledges support from ALMA-CONICYT project number 31110002 and D.M., from FONDECYT No. 1130196. M.G. is financed by the GEMINI-CONICYT Fund, allocated to Project 32110014. D.G. gratefully acknowledges support from the Chilean BASAL Centro de Excelencia en Astrofísica y Tecnologías Afines (CATA) grant PFB-06/2007. R.K.S. acknowledges partial support from FONDECYT through grant 1130140, and CNPq/Brazil through projects 310636/2013-2 and 481468/2013-7. M.C. acknowledges additional support from FONDECYT through grants #1110326 and 1141141. The work of I.N. and A.M. is partially supported by the Spanish Ministerio de Economía y Competitividad (Mineco) under grant AYA2012-39364-C02-02.