Detections of Compact Radio Continuum toward Methanol Maser Rings Using the VLA

TL;DR

This study uses the VLA to detect and image radio continuum emission associated with methanol maser rings in high-mass protostars, revealing thermal jets and complex structures that inform star formation processes.

Contribution

First high-resolution radio continuum images of methanol maser ring regions, identifying thermal jets and complex emission structures in high-mass star-forming regions.

Findings

Detected thermal jets in four sources.

Identified complex emission in one source, possibly from multiple protostars.

Associated some radio emission with evolved H II regions.

Abstract

High-mass protostars are deeply embedded in dust inside their natal cores and are not easily detectable. However, maser emission at centimeter wavelengths, owing to its high brightness, enables us to study gas kinematics in protostars' circumstellar regions. We aim to understand the origin of the ring-like structures outlined by the 6.7 GHz methanol maser emission in six high-mass young stellar objects by performing a sensitive search of the associated radio-continuum emission and derive its properties. We used the Karl G. Jansky Very Large Array in the A configuration at C and K bands in order to image radio-continuum as well as 6.7 GHz methanol and 22 GHz water maser emission. We present the first images of the thermal jets towards four targets in our sample, G23.389+00.185, G23.657-00.127, G28.817+00.365, and G30.400-00.296. In a further target, G23.207-00.377, the complex K band continuum emission makes it unclear whether the detected peaks trace jet knots from a single young protostar or mark multiple compact young protostars. The remaining source G31.047+00.356 shows radio continuum emission associated with an evolved H II region.