The Embedded Massive Star Forming Region RCW 38

RCW 38 is a uniquely young (<1 Myr), embedded (AV ∼ 10) stellar cluster surrounding a pair of early O stars (∼O5.5) and is one of the few regions within 2 kpc other than Orion to contain over 1000 members. X-ray and deep near-infrared observations reveal a dense cluster with over 200 X-ray sources and 400 infrared sources embedded in a diffuse hot plasma within a 1 pc diameter. The central O star has evacuated its immediate surroundings of dust, creating a wind bubble ∼0.1 pc in radius that is confined by the surrounding molecular cloud, as traced by millimeter continuum and molecular line emission. The interface between the bubble and cloud is a region of warm dust and ionized gas, which shows evidence for ongoing star formation. Extended warm dust is found throughout a 2–3 pc region and coincides with extended X-ray plasma. This is evidence that the influence of the massive stars reaches beyond the confines of the O star bubble. RCW 38 appears similar in structure to RCW 49 and M 20 but is at an earlier evolutionary phase. RCW 38 appears to be a blister compact HII region lying just inside the edge of a giant molecular cloud. Figure 1. An optical image of RCW 38, about 20 (∼10 pc) on a side, based on images from the digitized sky survey (DSS). Blue plates are printed as blue, red plates are printed as yellow, near-infrared data are printed in red. The region in the green box is shown at mid-infrared wavelengths in Figure 2.