Rotation of the Warm Molecular Gas Surrounding Ultracompact HII Regions

TL;DR

This study uses high-resolution observations to reveal that warm molecular gas around ultracompact HII regions exhibits bulk rotation, providing insights into the dynamics of massive star-forming regions.

Contribution

First detailed high-resolution analysis showing bulk rotation of warm molecular gas around ultracompact HII regions.

Findings

Warm molecular gas shows bulk rotation around HII regions.

Gas mass estimates are consistent across methods.

Stellar mass estimates are significant fractions of dynamical mass.

Abstract

We present molecular line and 1.4 mm continuum observations towards five massive star forming regions at arcsecond resolution using the Submillimeter Array (SMA). We find that the warm molecular gas surrounding each HII region (as traced by SO_2 and OCS) appears to be undergoing bulk rotation. From the molecular line emission and thermal component of the continuum emission, we independently derived gas masses for each region which are consistent with each other. From the free-free component of the continuum emission we estimate the minimum stellar mass required to power the HII region and find that this mass, when added to the derived gas mass, is a significant fraction of the dynamical mass for that region.