New class I methanol masers

Abstract

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 at the ALMA frequency range.

8 pages, 2 figures, to appear in proceedings for IAUS 287: Cosmic Masers - from OH to H0

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Cited by in corpus (6)

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• Approaching hell's kitchen: Molecular daredevil clouds in the vicinity of Sgr A*
• The warm-up phase in massive star-forming cores around RCW 120
• The methanol emission in the $J_1-J_0$ A${}^{-+}$ line series as a tracer of specific physical conditions in high-mass star-forming regions
• Spectral survey of a Hot core with an Eruptive Accretion in S255IR NIRS3 (SHEA): The discovery of class I and class II millimeter methanol maser transitions
• Gas-phase and Surface Chemistry in the Massive Star-Forming Region RCW\,120