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A search for 4750- and 4765-MHz OH masers in southern star-forming regions
journal contribution
posted on 2023-05-16, 13:26 authored by Dodson, R, Simon EllingsenSimon EllingsenWe have used the Australia Telescope Compact Array (ATCA) to make a sensitive (5σ ≃ 100 mJy) search for maser emission from the 4765-MHz 2Π1/2 F = 1 → 0 transition of OH. 55 star formation regions were searched and maser emission with a peak flux density in excess of 100 mJy was detected toward 14 sites, with 10 of these being new discoveries. In addition we observed the 4750-MHz 2Π1/2 F = 1 → 1 transition towards a sample of star formation regions known to contain 1720-MHz OH masers, detecting marginal maser emission from G348.550-0.979. If confirmed this would be only the second maser discovered from this transition. The occurrence of 4765-MHz OH maser emission accompanying 1720-MHz OH masers in a small number of well-studied star formation regions has led to a general perception in the literature that the two transitions favour similar physical conditions. Our search has found that the presence of the excited-state 6035-MHz OH transition is a much better predictor of 4765-MHz OH maser emission from the same region than 1720-MHz OH maser emission is. Combining our results with those of previous high-resolution observations of other OH transitions we have examined the published theoretical models of OH masers and find that none of them predicts any conditions in which the 1665-, 6035- and 4765-MHz transitions are inverted simultaneously.
History
Publication title
Monthly Notices of the Royal Astronomical SocietyVolume
333Pagination
307-317ISSN
0035-8711Department/School
School of Natural SciencesPublisher
Blackwell Publishing LtdPlace of publication
Oxford, EnglandRepository Status
- Restricted