3 research outputs found

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

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    We have investigated the central region of NGC 253 for the presence of 84.5-GHz (5βˆ’1β†’405_{-1}\rightarrow4_0E) 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 4βˆ’1β†’304_{-1}\rightarrow3_0E and 44.1-GHz 70β†’617_{0}\rightarrow6_1A+^{+} methanol lines) . The emission features a narrow linewidth (∼\sim12 km sβˆ’1^{-1}) with a luminosity approximately 5 orders of magnitude higher than typical Galactic sources. We determine an integrated line intensity ratio of 1.2Β±0.41.2\pm0.4 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.Comment: Accepted into ApJL 12 October 2018. 10 pages, 3 Figures and 2 Table