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

Voronkov, M.A., Walsh, A.J., Caswell, J.L., Ellingsen, S.P., Breen, S.L., Longmore, S.N., Purcell, C.R., Urquhart, J.S. (2011) 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 0035-8711. (doi:10.1111/j.1365-2966.2011.18297.x) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided)

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http://www.dx.doi.org/10.1111/j.1365-2966.2011.182...

Abstract

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 25GHz. The Australia Telescope Compact Array (ATCA) was used to follow up these detections at high angular resolution and prove the maser nature of the observed emission. The analysis shows that the new methanol maser at 23.4GHz 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 0.5arcsec) in the vicinity of the dominant infrared source, but at a clearly distinct position from nearby OH, H2O and class II methanol masers at 6.7GHz. 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 (1.3mJy) continuum source at 25GHz 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 Type: Article
DOI/Identification number: 10.1111/j.1365-2966.2011.18297.x
Uncontrolled keywords: ISM: molecules, Masers
Subjects: Q Science > QB Astronomy > QB460 Astrophysics
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: James Urquhart
Date Deposited: 30 Nov 2015 16:02 UTC
Last Modified: 29 May 2019 16:28 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/52223 (The current URI for this page, for reference purposes)
Urquhart, J.S.: https://orcid.org/0000-0002-1605-8050
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