Evidence for Co-Propagation of 4765- and 1720-MHz OH Masers in Star-Forming Regions |
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| Authors: | A Niezurawska M Szymczak A M S Richards R J Cohen |
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| Institution: | (1) Toru Centre for Astronomy, Nicolaus Copernicus University, Gagarina, Toru, Poland;(2) Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire, UK |
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| Abstract: | Two star-forming regions Cepheus A and W75N, were searched for the 4765-MHz OH maser emission using the multi-element radio linked interferometer network (MERLIN). The excited OH emission has an arc-like structure of 40 mas in Cep A and a linear structure of size 45 mas in W75N. We also found the 1720-MHz line in Cep A and Hutawarakorn MNRAS 330 (2002) 349] reported the 1720-MHz emission in W75N. The 1720- and 4765-MHz OH spots coincided in space within 60 mas and in velocity within 0.3 km s–1 in both targets implying that both maser transitions arise from the same region. According to the modelling by Gray MNRAS 252 (1991) 30] the 1720/4765-MHz co-propagation requires a low density, warm environment. The masers lie at the edges of H II regions where such conditions are expected. |
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| Keywords: | masers stars: formation ISM: molecules radio lines: ISM H II regions |
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