Investigation of Diffuse Hard X-ray Emission from the Massive Star-Forming Region NGC 6334

Abstract

Chandra ACIS-I data of the molecular cloud and HII region complex NGC 6334 were analyzed. The hard X-ray clumps detected with ASCA (Sekimoto et al. 2000) were resolved into 792 point sources. After removing the point sources, an extended X-ray emission component was detected over a 5x9 pc2 region, with the 0.5-8 keV absorption-corrected luminosity of 2x10^33 erg/s. The contribution from faint point sources to this extended emission was estimated as at most ~20 %, suggesting that most of the emission is diffuse in nature. The X-ray spectrum of the diffuse emission was observed to vary from place to place. In tenuous molecular cloud regions with hydrogen column density of 0.5~1x10^22 cm-2, the spectrum can be represented by a thermal plasma model with temperatures of several keV. The spectrum in dense cloud cores exhibits harder continuum, together with higher absorption more than ~3x10^22 cm-2. In some of such highly obscured regions, the spectrum show extremely hard continua equivalent to a photon index of ~1, and favor non-thermal interpretation. These results are discussed in the context of thermal and non-thermal emissions, both powered by fast stellar winds from embedded young early-type stars through shock transitions.