A search for 85.5- and 86.6-GHz methanol maser emission

Abstract

We have used the Australia Telescope National Facility Mopra 22m millimetre telescope to search for emission from the 85.5-GHz and 86.6-GHz transitions of methanol. The search was targeted towards 22 star formation regions which exhibit maser emission in the 107.0-GHz methanol transition, as well as in the 6.6-GHz transition characteristic of class II methanol maser sources. A total of 22 regions were searched at 85.5 GHz resulting in 5 detections, of which 1 appears to be a newly discovered maser. For the 86.6-GHz transition observations were made of 18 regions which yielded 2 detections, but no new maser sources. This search demonstrates that emission from the 85.5- and 86.6-GHz transitions is rare. Detection of maser emission from either of these transitions therefore indicates the presence of special conditions, different from those in the majority of methanol maser sources. We have observed temporal variability in the 86.6-GHz emission towards 345.010+1.792, which along with the very narrow line width, confirms that the emission is a maser in this source. We have combined our current observations with published data for the 6.6-, 12.1-, 85.5-, 86.6-, 107.0-, 108.8- and 156.6-GHz transitions for comparison with the maser model of Sobolev & Deguchi (1994). This has allowed us to estimate the likely ranges of dust temperature, gas density, and methanol column density, both for typical methanol maser sources and for those sources which also show 107.0-GHz emission.

arXiv comment11 pages, accepted for publication in MNRAS, Latex, mn2e.cls

References in corpus (3)

• A Survey of the Galactic Plane for 6.7-GHz Methanol Masers I: l = 325.0 - 335.0 ; b = -0.53 - 0.53
• Multi-transition study and new detections of class II methanol masers
• Detection of new sources of methanol emission at 107 and 108 GHz with the Mopra telescope

Cited by in corpus (14)

• A general catalogue of 6.7 GHz methanol masers. I: data
• Water masers accompanying OH and methanol masers in star formation regions
• Discovery of six new class II methanol maser transitions, including the unambiguous detection of three torsionally excited lines toward G358.931-0.030
• 37 GHz methanol masers : Horsemen of the Apocalypse for the class II methanol maser phase?
• Discovery of new 19.9-GHz methanol masers in star forming regions
• 12.2-GHz methanol maser MMB follow-up catalogue - II. Longitude range 186 to 330 degrees
• 84-GHz methanol masers, their relationship to 36-GHz methanol masers and their molecular environments
• Testing maser-based evolutionary schemes: A new search for 37.7-GHz methanol masers
• Discovery of Two New Class II Methanol Maser Transitions in G345.01+1.79
• The first high-resolution observations of 19.9-GHz methanol masers
• The first high-resolution observations of 37.7-, 38.3- and 38.5-GHz methanol masers
• Evolution of HII regions in hierarchically structured molecular clouds
• Masers and star formation
• A sensitive search for predicted methanol maser transitions with the Australia Telescope Compact Array