1596 Dawson.pdf (36.98 MB)
SPLASH: the Southern Parkes Large-Area Survey in Hydroxyl – first science from the pilot region
journal contribution
posted on 2023-05-17, 23:33 authored by Joanne Dawson, Walsh, AJ, Jones, PA, Breen, SL, Cunningham, MR, Lowe, V, Jones, C, Purcell, C, Caswell, JL, Carretti, E, McClure-Griffiths, NM, Simon EllingsenSimon Ellingsen, Green, JA, Gomez, JF, Krishnan, V, John DickeyJohn Dickey, Imai, H, Gibson, SJ, Hennebelle, P, Lo, N, Hayakawa, T, Fukui, Y, Mizuno, AThe Southern Parkes Large-Area Survey in Hydroxyl (SPLASH) is a sensitive, unbiased, and fully sampled survey of the southernGalactic plane and Galactic Centre in all four ground-state transitions of the hydroxyl (OH) radical. The survey provides a deep census of 1612-, 1665-, 1667-, and 1720-MHz OH absorption and emission from the Galactic interstellar medium, and is also an unbiased search for maser sources in these transitions. We present here first results from the SPLASH pilot region, which covers Galactic longitudes 334° to 344° and latitudes ±2°. Diffuse OH is widely detected in all four transitions, with optical depths that are always small (averaged over the Parkes beam), and with departures from local thermodynamic equilibrium common even in the 1665- and 1667-MHz main lines. To a 3σ sensitivity of ∼30 mK, we find no evidence of OH envelopes extending beyond the CO-bright regions of molecular cloud complexes, and conclude that the similarity of the OH excitation temperature and the level of the continuum background is at least partly responsible for this. We detect masers and maser candidates in all four transitions, approximately 50 per cent of which are new detections. This implies that SPLASH will produce a substantial increase in the known population of ground-state OH masers in the southern Galactic plane.
Funding
Australian Research Council
History
Publication title
Monthly Notices of the Royal Astronomical SocietyVolume
439Pagination
1596-1614ISSN
0035-8711Department/School
School of Natural SciencesPublisher
Blackwell Publishing LtdPlace of publication
9600 Garsington Rd, Oxford, England, Oxon, Ox4 2DgRights statement
Copyright 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical SocietyRepository Status
- Open