New 9.9-GHz methanol masers

TL;DR

This study used the ATCA to conduct the first extensive search for 9.9-GHz class I methanol masers in 48 high-mass star formation regions, discovering two new masers and providing precise positions.

Contribution

It reports the first large-scale survey for 9.9-GHz methanol masers and identifies new maser sources, expanding understanding of their association with star formation stages.

Findings

Two new 9.9-GHz masers discovered.

Class I masers may persist longer than class II masers.

Masers are possibly linked to shocks from HII regions.

Abstract

The Australia Telescope Compact Array (ATCA) has been used to make the first extensive search for the class I methanol masers at 9.9 GHz. In total, 48 regions of high-mass star formation were observed. In addition to masers in W33-Met (G12.80-0.19) and G343.12-0.06 (IRAS 16547-4247) which have already been reported in the literature, two new 9.9-GHz masers have been found towards G331.13-0.24 and G19.61-0.23. We have determined absolute positions (accurate to roughly a second of arc) for all the detected masers and suggest that some class I masers may be associated with shocks driven into molecular clouds by expanding HII regions. Our observations also imply that the evolutionary stage of a high-mass star forming region when the class I masers are present can outlast the stage when the class II masers at 6.7 GHz are detectable, and overlaps significantly with the stage when OH masers are active.