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Abstract

We have investigated the central region of NGC 253 for the presence of 84.5 GHz (5−1 → 40E) methanol emission using the Australia Telescope Compact Array. We present the second detection of 84.5 GHz class I methanol maser emission outside of the Milky Way. This maser emission is offset from the dynamical center of NGC 253, in a region with previously detected emission from class I maser transitions (36.2 GHz 4−1 → 30E and 44.1 GHz 70 → 61A+ methanol lines). The emission features a narrow linewidth (~12 ) with a luminosity approximately that is 5 orders of magnitude higher than typical Galactic sources. We determine an integrated line intensity ratio of 1.2 ± 0.4 between the 36.2 and 84.5 GHz class I methanol maser emission, which is similar to the ratio observed toward Galactic sources. The three methanol maser transitions observed toward NGC 253 each show a different distribution, suggesting differing physical conditions between the maser sites, and also that observations of additional class I methanol transitions will facilitate investigations of the maser pumping regime.

Item Type:	Article
Authors/Creators:	McCarthy, TP and Ellingsen, SP and Breen, SL and Voronkov, MA and Chen, X
Keywords:	galaxies: individual (NGC 253), galaxies: starburst, masers, radio lines: galaxies
Journal or Publication Title:	The Astrophysical Journal Letters
Publisher:	Institute of Physics Publishing Ltd.
ISSN:	2041-8205
DOI / ID Number:	10.3847/2041-8213/aae82c
Copyright Information:	Copyright 2018 The American Astronomical Society
Related URLs:	Google Scholar: Ellingsen, SP UTAS Profile: Ellingsen, SP
Item Statistics:	View statistics for this item

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