The Embedded Massive Star Forming Region RCW 38

TL;DR

RCW 38 is a very young, dense star-forming region within 2 kpc, featuring massive stars, a dense cluster, and evidence of ongoing star formation influenced by stellar winds and hot plasma.

Contribution

This study provides detailed multi-wavelength observations revealing the structure, star formation activity, and feedback processes in RCW 38, an early evolutionary stage of massive star-forming regions.

Findings

Over 200 X-ray sources and 400 infrared sources identified.

Presence of a wind bubble around the central O star.

Evidence of ongoing star formation at the bubble-cloud interface.

Abstract

RCW~38 is a uniquely young ($<$1 Myr), embedded ($A_V \sim 10$) stellar cluster surrounding a pair of early O stars ($\sim$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 $\sim$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 H{\small II} region lying just inside the edge of a giant molecular cloud.