A first look at the x-ray population of the young massive cluster VVV cl077

Abstract

Multi-wavelength analysis of the young massive cluster VVV CL077 is presented for the first time. Our Chandra survey of this region enabled the detection of three X-ray emitting stellar members of the cluster, as well as a possible diffuse X-ray component that extends a few arcseconds from the cluster core with an intrinsic flux of (9 ± 3) × 10-14 erg cm-2 s-1 in the 0.5-10 keV band. Infrared spectra we obtained for two of these X-ray point sources show absorption lines typical of the atmospheres of massive O stars. The X-ray spectrum from the visible extent of VVV CL077 i.e., a 15″ radius around the cluster, can be modeled with an absorbed power law with N H (6+4-3) × 10-10 cm-2 and Γ = 2 ± 1. In addition, the X-ray core of VVV CL077 coincides with diffuse emission seen in the infrared band and with a local maximum in the radio continuum map. A possible association with a neighboring H II region would place VVV CL077 at a distance of around 11 kpc, on the far side of the Norma Arm. At this distance, the cluster is 0.8 pc wide with a mass density of (1-4) × 103 M⊙pc-3.