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Variability in extragalactic class I methanol masers: new maser components towards NGC 4945 and NGC 253

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McCarthy, TP, Ellingsen, SP ORCID: 0000-0002-1363-5457, Breen, SL, Voronkov, MA, Chen, X and Qiao, H-h 2020 , 'Variability in extragalactic class I methanol masers: new maser components towards NGC 4945 and NGC 253' , Monthly Notices of the Royal Astronomical Society, vol. 491, no. 4 , pp. 4642-4655 , doi: 10.1093/mnras/stz3098.

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Abstract

We have used the Australia Telescope Compact Array (ATCA) to make new observations of the 36.2-GHz (4−1 → 30E) methanol transition towards NGC 4945 and NGC 253. These observations have revealed the presence of new maser components towards these galaxies, and have provided the first clear evidence for variability in extragalactic class I methanol masers. Alongside the new observations of NGC 4945 and NGC 253, we present the results of recent 36.2-GHz methanol maser searches towards 12 galaxies, placing upper limits on the emission from the 36.2-GHz class I transition and the 37.7-GHz (72 → 81E) class II maser line towards these sources. Flux density values for the 7-mm continuum emission towards these sources are also reported where applicable. A re-analysis of the published 36.2-GHz methanol observations of Arp 220 undertaken as part of the search revealed some issues with previous imaging procedures. The re-analysis, combined with non-detections in independent follow-up observations, suggests that there is no 36.2-GHz methanol emission towards Arp 220 stronger than 3.5 mJy in a 10 km s−1 channel (5σ upper limit).

Item Type: Article
Authors/Creators:McCarthy, TP and Ellingsen, SP and Breen, SL and Voronkov, MA and Chen, X and Qiao, H-h
Keywords: masers; galaxies: starburst; radio lines: galaxies
Journal or Publication Title: Monthly Notices of the Royal Astronomical Society
Publisher: Blackwell Publishing Ltd
ISSN: 0035-8711
DOI / ID Number: 10.1093/mnras/stz3098
Copyright Information:

Copyright 2020 P.K. Humire et al. Licensed under Creative Commons Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/

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