An X-ray imaging study of the stellar population in RCW 49

We present the results of a high-resolution X-ray imaging study of the stellar population in the Galactic massive star-forming region RCW 49 and its central OB association Westerlund 2. We obtained a similar to 40 ks X-ray image of a similar to 17' x 17' field using the Chandra X-Ray Observatory and deep NIR images using the Infrared Survey Facility in a concentric similar to 8.3' x 8.3' region. We detected 468 X-ray sources and identified optical, NIR, and Spitzer MIR counterparts for 379 of them. The unprecedented spatial resolution and sensitivity of the X-ray image, enhanced by optical and infrared imaging data, yielded the following results: ( 1) The central OB association Westerlund 2 is resolved for the first time in the X-ray band. X-ray emission is detected from all spectroscopically identified early-type stars in this region. ( 2) Most ( similar to 86%) X-ray sources with optical or infrared identifications are cluster members in comparison with a control field in the Galactic plane. ( 3) A loose constraint ( 2-5 kpc) for the distance to RCW49 is derived from the mean X- ray luminosity of T Tauri stars. ( 4) The cluster X- ray population consists of low-mass pre-main-sequence and early-type stars as obtained from X- ray and NIR photometry. About 30 new OB star candidates are identified. ( 5) We estimate a cluster radius of 6'-7' based on the X- ray surface number density profiles. ( 6) A large fraction ( similar to 90%) of cluster members are identified individually using complimentary X- ray and MIR excess emission. ( 7) The brightest five X-ray sources, two Wolf-Rayet stars and three O stars, have hard thermal spectra.