Studies of methanol maser rings

TL;DR

This study investigates a new class of 6.7 GHz methanol maser sources with ring-like structures, revealing their close association with early-stage massive star formation through multi-wavelength observations.

Contribution

It provides the first detailed multi-wavelength analysis of methanol maser rings, linking their structure to early massive star formation stages.

Findings

Methanol maser rings are closely associated with mid-infrared emission peaks.

Ring centers are within 0.2 arcseconds of MIR emission peaks, indicating a physical connection.

Methanol rings appear before water maser outflows or H II regions are detectable.

Abstract

We present the results of studies of a new class of 6.7 GHz methanol maser sources with a ring-like emission structure discovered recently with the EVN. We have used the VLA to search for water masers at 22 GHz and radio continuum at 8.4 GHz towards a sample of high-mass star forming regions showing a ring-like distribution of methanol maser spots. Using the Gemini telescopes we found mid-infrared (MIR) counterparts of five methanol rings with a resolution of 0."15. The centres of methanol maser rings are located within, typically, only 0."2 of the MIR emission peak, implying their physical relation with a central star. These results strongly support a scenario wherein the ring-like structures appear at the very early stage of massive star formation before either water-maser outflows or H II regions are seen.