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MALT-45: a 7mm survey of the southern Galaxy - II. ATCA follow-up observations of 44GHz class I methanol masers


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Jordan, CH, Walsh, AJ, Breen, SL, Ellingsen, SP ORCID: 0000-0002-1363-5457, Voronkov, MA and Hyland, LJ 2017 , 'MALT-45: a 7mm survey of the southern Galaxy - II. ATCA follow-up observations of 44GHz class I methanol masers' , Monthly Notices of the Royal Astronomical Society, vol. 471, no. 4 , pp. 3915-3954 , doi: 10.1093/mnras/stx1776.

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We detail interferometric observations of 44 GHz class I methanol masers detected by MALT-45 (a 7 mm unbiased auto-correlated spectral-line Galactic-plane survey) using the Australia Telescope Compact Array. We detect 238 maser spots across 77 maser sites. Using high-resolution positions, we compare the class I CH3OH masers to other star formation maser species, including CS (1–0), SiO v = 0 and the H53 α radio-recombination line. Comparison between the cross- and auto-correlated data has allowed us to also identify quasi-thermal emission in the 44 GHz class I methanol maser line. We find that the majority of class I methanol masers have small spatial and velocity ranges (−1), and closely trace the systemic velocities of associated clouds. Using 870 μm dust continuum emission from the ATLASGAL survey, we determine clump masses associated with class I masers, and find that they are generally associated with clumps between 1000 and 3000 M⊙. For each class I methanol maser site, we use the presence of OH masers and radio recombination lines to identify relatively evolved regions of high-mass star formation; we find that maser sites without these associations have lower luminosities and preferentially appear towards dark infrared regions.

Item Type: Article
Authors/Creators:Jordan, CH and Walsh, AJ and Breen, SL and Ellingsen, SP and Voronkov, MA and Hyland, LJ
Keywords: masers, surveys, stars: formation, ISM: molecules, galaxy: structure, radio lines: ISM
Journal or Publication Title: Monthly Notices of the Royal Astronomical Society
Publisher: Blackwell Publishing Ltd
ISSN: 0035-8711
DOI / ID Number: 10.1093/mnras/stx1776
Copyright Information:

This article has been accepted for publication in Royal Astronomical Society. Monthly Notices. Copyright 2017 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.

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