Radio Continuum and Methanol Observations of DR21(OH)

TL;DR

This study uses high-resolution radio observations to analyze the star-forming region DR21(OH), revealing new methanol masers, radio sources, and insights into outflow and jet orientations related to star formation processes.

Contribution

First detailed high-resolution radio and methanol maser observations of DR21(OH), identifying new maser components and clarifying outflow and jet structures.

Findings

Discovered over 30 new methanol maser components.

Identified a cluster of radio sources with the strongest in MM1.

Suggested the outflow driver is likely in the MM2 core.

Abstract

We report high sensitivity sub-arcsecond angular resolution observations of the massive star forming region DR21(OH) at 3.6, 1.3, and 0.7 cm obtained with the Very Large Array. In addition, we conducted observations of CH3OH 44 GHz masers. We detected more than 30 new maser components in the DR21(OH) region. Most of the masers appear to trace a sequence of bow-shocks in a bipolar outflow. The cm continuum observations reveal a cluster of radio sources; the strongest emission is found toward the molecular core MM1. The radio sources in MM1 are located about 5" north of the symmetry center of the CH3OH outflow, and therefore, they are unlikely to be associated with the outflow. Instead, the driving source of the outflow is likely located in the MM2 core. Although based on circumstantial evidence, the radio continuum from MM1 appears to trace free-free emission from shock-ionized gas in a jet. The orientation of the putative jet in MM1 is approximately parallel to the CH3OH outflow and almost perpendicular to the large scale molecular filament that connects DR21 and DR21(OH). This suggests that the (accretion) disks associated with the outflows/jets in the DR21 - DR21(OH) region have symmetry axes mostly perpendicular to the filament.