High Resolution CO Observations of Massive Star Forming Regions

TL;DR

This study uses high-resolution CO observations to analyze gas dynamics in three massive star-forming regions, revealing large-scale outflows and infall, and clarifying the sources responsible for these structures.

Contribution

It provides detailed high-resolution observations linking large-scale gas structures to specific protostars within HII regions, advancing understanding of massive star formation processes.

Findings

Large outflows (0.26-0.40 pc) driven by protostars near HII regions.

Detected infall signatures with rates around 10^-4 M_sun/yr.

Star formation persists despite the presence of HII regions.

Abstract

Context. To further understand the processes involved in the formation of massive stars, we have undertaken a study of the gas dynamics surrounding three massive star forming regions. By observing the large scale structures at high resolution, we are able to determine properties such as driving source, and spatially resolve the bulk dynamical properties of the gas such as infall and outflow. Aims. With high resolution observations, we are able to determine which of the cores in a cluster forming massive stars is responsible for the large scale structures. Methods. We present CO observations of three massive star forming regions with known HII regions and show how the CO traces both infall and outflow. By combining data taken in two SMA configurations with JCMT observations, we are able to see large scale structures at high resolution. Results. We find large (0.26-0.40 pc), massive (2-3 M_sun) and energetic (13-17 \times 10^44 erg) outflows emanating from the edges of two HII regions suggesting they are being powered by the protostar(s) within. We find infall signatures in two of our sources with mass infall rates of order 10-4 M_sun/yr. Conclusions. We suggest that star formation is ongoing in these sources despite the presence of HII regions. We further conclude that the source(s) within a single HII region are responsible for the observed large scale structures; that these large structures are not the net effect of multiple outflows from multiple HII regions and hot cores.