New class i methanol masers

M. A. Voronkov*, J. L. Caswell, S. P. Ellingsen, S. L. Breen, T. R. Britton, J. A. Green, A. M. Sobolev, A. J. Walsh

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference proceeding contribution

3 Citations (Scopus)


We review properties of all known collisionally pumped (class I) methanol maser series based on observations with the Australia Telescope Compact Array (ATCA) and the Mopra radio telescope. Masers at 36, 84, 44 and 95 GHz are most widespread, while 9.9, 25, 23.4 and 104 GHz masers are much rarer, tracing the most energetic shocks. A survey of many southern masers at 36 and 44 GHz suggests that these two transitions are highly complementary. The 23.4 GHz maser is a new type of rare class I methanol maser, detected only in two high-mass star-forming regions, G357.97-0.16 and G343.12-0.06, and showing a behaviour similar to 9.9, 25 and 104 GHz masers. Interferometric positions suggest that shocks responsible for class I masers could arise from a range of phenomena, not merely an outflow scenario. For example, some masers might be caused by interaction of an expanding Hii region with its surrounding molecular cloud. This has implications for evolutionary sequences incorporating class I methanol masers if they appear more than once during the evolution of the star-forming region. We also make predictions for candidate maser transitions in the ALMA frequency range.

Original languageEnglish
Title of host publicationCosmic Masers - from OH to H0
EditorsRoy S. Booth, Elizabeth M. L. Humphreys, Wouter H. T. Vlemmings
Place of PublicationCambridge, England
PublisherCambridge University Press
Number of pages8
ISBN (Print)9781107032842
Publication statusPublished - Jul 2012

Publication series

NameProceedings of the International Astronomical Union
ISSN (Print)17439213
ISSN (Electronic)17439221


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