Detection of 84-GHz class I methanol maser emission towards NGC 253

Abstract

We have investigated the central region of NGC 253 for the presence of 84.5-GHz ($5_{-1}\to 4_0$E) methanol emission using the Australia Telescope Compact Array. We present the second detection of 84.5-GHz class~I methanol maser emission outside the Milky Way. This maser emission is offset from dynamical centre of NGC 253, in a region with previously detected emission from class~I maser transitions (36.2-GHz $4_{-1}\to 3_0$E and 44.1-GHz $7_0\to 6_1$A${}^{+}$ methanol lines) . The emission features a narrow linewidth ($\sim$12 km s${}^{-1}$) with a luminosity approximately 5 orders of magnitude higher than typical Galactic sources. We determine an integrated line intensity ratio of $1.2\pm 0.4$ between the 36.2 GHz and 84.5-GHz class I methanol maser emission, which is similar to the ratio observed towards 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 that observations of additional class~I methanol transitions will facilitate investigations of the maser pumping regime.

arXiv commentAccepted into ApJL 12 October 2018. 10 pages, 3 Figures and 2 Tables

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Cited by in corpus (4)

• Online Database of Class I Methanol Masers
• Methanol masers in NGC 253 with ALCHEMI
• 36 GHz methanol lines from nearby galaxies: maser or quasi-thermal emission?
• Variability in extragalactic class I methanol masers: New maser components toward NGC4945 and NGC253