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Discovery of the new class I methanol maser transition at 23.4 GHz


Voronkov, MA and Walsh, AJ and Caswell, JL and Ellingsen, SP and Breen, SL and Longmore, SN and Purcell, CR and Urquhart, JS, Discovery of the new class I methanol maser transition at 23.4 GHz, Monthly Notices of the Royal Astronomical Society, 413, (4) pp. 2339-2344. ISSN 1365-2966 (2011) [Refereed Article]

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DOI: doi:10.1111/j.1365-2966.2011.18297.x


We report the first detection of a methanol maser in the 101–92 A− transition at 23.4 GHz, discovered during the H2O southern Galactic Plane Survey (HOPS) with the 22-m Mopra Radio Telescope. In the region covered by HOPS, the 23.4-GHz maser was found at only one location, G357.97−0.16, which was also a prominent source of maser emission in the J2–J1 E series near 25 GHz. The Australia Telescope Compact Array (ATCA) was used to followup these detections at high angular resolution and prove the maser nature of the observed emission. The analysis shows that the new methanol maser at 23.4 GHz is a class I maser, which has properties similar to the 9.9- and 25-GHz masers (i.e. traces strong shocks with higher than average temperature and density). All class I masers were found to originate at the same spatial location (within the measurement uncertainty of 0.5 arcsec) in the vicinity of the dominant infrared source, but at a clearly distinct position from nearby OH, H2O and class II methanol masers at 6.7 GHz. All maser species are distributed approximately on a line, but it is not clear at present whether this has any physical significance. We also detected a weak (1.3 mJy) continuum source at 25 GHz near the OH maser (at the most northern site, associated with a class II methanol maser and an H2O maser renowned for its extremely wide spread of velocity components). The continuum source has not been reported at lower frequencies and is therefore a candidate hypercompact HII region.We also used the ATCA to find the strongest and only the fifth known 9.9-GHz maser towards G357.97−0.16 and another 23.4-GHz maser towards G343.12−0.06 not seen in HOPS.

Item Details

Item Type:Refereed Article
Keywords:masers – ISM: molecules
Research Division:Physical Sciences
Research Group:Astronomical sciences
Research Field:Galactic astronomy
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the physical sciences
UTAS Author:Ellingsen, SP (Professor Simon Ellingsen)
UTAS Author:Breen, SL (Dr Shari Breen)
ID Code:68822
Year Published:2011
Web of Science® Times Cited:13
Deposited By:Mathematics and Physics
Deposited On:2011-03-24
Last Modified:2017-11-03

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