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2002MNRAS.331..521C - Mon. Not. R. Astron. Soc., 331, 521-536 (2002/April-1)
Modelling methanol and hydroxyl masers in star-forming regions.
CRAGG D.M., SOBOLEV A.M. and GODFREY P.D.
Abstract (from CDS):
We find the gas-phase molecular abundance to be the key determinant of observable maser activity for both molecules. Sources exhibiting both 6668-MHz methanol and 1665-MHz OH masers have a typical flux density ratio of 16; our model suggests that this may be a consequence of maser saturation. We find that the 1665-MHz maser approaches the saturated limit for OH abundances >10–7.3, while the 6668-MHz maser requires a greater methanol abundance >10–6. OH-favoured sources are likely to be less abundant in methanol, while methanol-favoured sources may be less abundant in OH or experiencing warm (>125K), dense (∼107 cm–3) conditions. These abundance requirements offer the possibility of tying the appearance of masers to the age of the new-born star via models of gas-phase chemical evolution following the evaporation of icy grain mantles.
Abstract Copyright: 2002 Blackwell Science Ltd
Journal keyword(s): masers - Hii regions - ISM: molecules - radio lines: ISM
Simbad objects: 3
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