paper

Molecular clouds toward three Spitzer bubbles S116, S117 and S118: Evidence for the cloud-cloud collision which formed the three \HII \ regions and a 10-pc scale molecular cavity

arXiv:1706.08720 · doi:10.1093/pasj/psy005

Abstract

We carried out a molecular line study toward the three Spitzer bubbles S116, S117 and S118 which show active formation of high-mass stars. We found molecular gas consisting of two components with velocity difference of { \kms}. One of them, the small cloud, has typical velocity of { \kms} \ and the other, the large cloud, has that of \kms. The large cloud has a nearly circular intensity depression whose size is similar to the small cloud. We present an interpretation that the cavity was created by a collision between the two clouds and the collision compressed the gas into a dense layer elongated along the western rim of the small cloud. In this scenario, the O stars including those in the three Spitzer bubbles were formed in the interface layer compressed by the collision. By assuming that the relative motion of the clouds has a tilt of \timeform{45D} to the line of sight, we estimate that the collision continued over the last 1 Myr at relative velocity of 10 \kms. In the S116--117--118 system the \HII \ regions are located outside of the cavity. This morphology is ascribed to the density-bound distribution of the large cloud which made the \HII \ regions more easily expand toward the outer part of the large cloud than inside of the cavity. The present case proves that a cloud-cloud collision creates a cavity without an action of O star feedback, and suggests that the collision-compressed layer is highly filamentary.

23 pages, 10 figures

References in corpus (5)

Cited by in corpus (25)