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We have searched for emission from the 36.2 GHz (4_-1 → 3₀E) methanol transition toward NGC 4945, using the Australia Telescope Compact Array. 36.2 GHz methanol emission was detected offset southeast from the Galactic nucleus. The methanol emission is narrow, with a line width <10 km s⁻¹ and a luminosity five orders of magnitude higher than Galactic class I masers from the same transition. These characteristics combined the with physical separation from the strong central thermal emission suggests that the methanol emission is a maser. This emission is a factor of ∼90 more luminous than the widespread emission detected from the Milky Way central molecular zone. This is the fourth detection of extragalactic class I emission and the third detection of extragalactic 36.2 GHz maser emission. These extragalactic class I methanol masers do not appear to be simply highly luminous variants of Galactic class I emission and instead appear to trace large-scale regions of low-velocity shocks in molecular gas, which may precede, or be associated with, the early stages of large-scale star formation.

Item Type:	Refereed Article
Keywords:	masers, galaxies: individual (NGC 4945), galaxies: starburst, radio lines: ISM
Research Division:	Physical Sciences
Research Group:	Astronomical sciences
Research Field:	Cosmology and extragalactic astronomy
Objective Division:	Expanding Knowledge
Objective Group:	Expanding knowledge
Objective Field:	Expanding knowledge in the physical sciences
UTAS Author:	McCarthy, TP (Dr Tiege McCarthy)
UTAS Author:	Ellingsen, SP (Professor Simon Ellingsen)
ID Code:	121201
Year Published:	2017
Web of Science® Times Cited:	13
Deposited By:	Mathematics and Physics
Deposited On:	2017-09-15
Last Modified:	2018-04-27
Downloads:	126 View Download Statistics