<i>WIDE-FIELD INFRARED SURVEY EXPLORER</i>OBSERVATIONS OF THE EVOLUTION OF MASSIVE STAR-FORMING REGIONS

TLDR

The study surveys 11 outer Galaxy massive star‑forming regions and 3 open clusters in the mid‑infrared with WISE to investigate their stellar content. The authors applied a new photometric method to identify young stellar objects and remove extragalactic contaminants, mapping their spatial distribution and examining WISE cutouts of peripheral structures. The observations support a fireworks‑like triggered star‑formation scenario, where winds and radiation from an initial massive‑star burst sculpt large pillar and trunk structures that host small clusters of Class I/II young stars.

Abstract

We present the results of a mid-infrared survey of 11 outer Galaxy massive star-forming regions and 3 open clusters with data from the Wide-field Infrared Survey Explorer (WISE). Using a newly developed photometric scheme to identify young stellar objects and exclude extragalactic contamination, we have studied the distribution of young stars within each region. These data tend to support the hypothesis that latter generations may be triggered by the interaction of winds and radiation from the first burst of massive star formation with the molecular cloud material leftover from that earlier generation of stars. We dub this process the "fireworks hypothesis" since star formation by this mechanism would proceed rapidly and resemble a burst of fireworks. We have also analyzed small cutout WISE images of the structures around the edges of these massive star-forming regions. We observe large (1–3 pc size) pillar and trunk-like structures of diffuse emission nebulosity tracing excited polycyclic aromatic hydrocarbon molecules and small dust grains at the perimeter of the massive star-forming regions. These structures contain small clusters of emerging Class I and Class II sources, but some are forming only a single to a few new stars.