Massive open star clusters using the VVV survey : V. Young clusters with an OB stellar population

Abstract

Context. The ESO public survey VISTA Variables in the Vía Láctea (VVV) has contributed with deep multi-epoch photometry of the Galactic bulge and the adjacent part of the disk over 526 sq. deg. More than a hundred cluster candidates have been reported thanks to this survey. Aims. We present the fifth article in a series of papers focused on young and massive clusters discovered in the VVV survey. In this paper, we present the physical characterization of five clusters with a spectroscopically confirmed OB-type stellar population. Methods. To characterize the clusters, we used near-infrared photometry (J, H, and KS) from the VVV survey and near-infrared K-band spectroscopy from ISAAC at VLT, following the methodology presented in the previous articles of the series. Results. All clusters in our sample are very young (ages between 1–20 Myr), and their total mass are between (1.07+0.40 −0.30) × 102 M and (4.17+4.15 −2.08) × 103 M . We observed a relation between the clusters total mass Mecl and the mass of their most massive stellar member mmax, for clusters with an age <10 Myr.