How do methanol masers manage to appear in the youngest star vicinities and isolated molecular clumps - AstrophysicsReport as inadecuate




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Abstract: General characteristics of methanol CH3OH maser emission are summarized. Itis shown that methanol maser sources are concentrated in the spiral arms. Mostof the methanol maser sources from the Perseus arm are associated with embeddedstellar clusters and a considerable portion is situated close to compact HIIregions. Almost 1-3 of the Perseus Arm sources lie at the edges of opticallyidentified HII regions which means that massive star formation in the PerseusArm is to a great extent triggered by local phenomena. A multiline analysis ofthe methanol masers allows us to determine the physical parameters in theregions of maser formation. Maser modelling shows that class II methanol maserscan be pumped by the radiation of the warm dust as well as by free-freeemission of a hypercompact region hcHII with a turnover frequency exceeding 100GHz. Methanol masers of both classes can reside in the vicinity of hcHIIs.Modelling shows that periodic changes of maser fluxes can be reproduced byvariations of the dust temperature by a few percent which may be caused byvariations in the brightness of the central young stellar object reflecting thecharacter of the accretion process. Sensitive observations have shown that themasers with low flux densities can still have considerable amplificationfactors. The analysis of class I maser surveys allows us to identify fourdistinct regimes that differ by the series of their brightest lines.



Author: A.M. Sobolev, D.M. Cragg, S.P. Ellingsen, M.J. Gaylard, S. Goedhart, C. Henkel, M.S. Kirsanova, A.B. Ostrovskii, N.V. Pankratova,

Source: https://arxiv.org/







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