Class I methanol masers in NGC253: Alcohol at the end of the bar

TL;DR

This study reports the detection of luminous class I methanol masers in NGC253, located at the galactic bar's end, likely caused by cloud collisions, and introduces the first extragalactic 44.1-GHz methanol maser.

Contribution

First detection of extragalactic 44.1-GHz class I methanol maser and analysis of its association with 36.2-GHz masers in NGC253, highlighting differences from Galactic star formation masers.

Findings

Masers located at the galactic bar's end, likely due to cloud collisions.

First extragalactic 44.1-GHz methanol maser detected.

Masers are significantly more luminous than those in Galactic regions.

Abstract

We have used the Australia Telescope Compact Array (ATCA) to observe the 36.2-GHz class I methanol maser emission towards NGC253 and find that it is located at the interface between the nuclear ring and both ends of the galactic bar. This is thought to be the location of the inner Linblad resonance and we suggest that the maser emission in this region is likely due to large-scale cloud-cloud collisions. We have detected the first extragalactic 44.1-GHz class I methanol maser and find that it is associated with the 36.2-GHz maser emission. In contrast to the class I methanol masers found in Galactic star formation regions, the 44.1-GHz emission in NGC253 is two orders of magnitude weaker than the 36.2-GHz masers. Both the 36.2- and 44.1- GHz emission is orders of magnitude stronger than expected from typical high-mass star formation regions. This demonstrates that the luminous class I methanol masers observed in NGC253 are significantly different from those associated with Galactic star formation.