SPLASH: the Southern Parkes Large-Area Survey in Hydroxyl - first science from the pilot region

J. R. Dawson*, A. J. Walsh, P. A. Jones, S. L. Breen, M. R. Cunningham, V. Lowe, C. Jones, C. Purcell, J. L. Caswell, E. Carretti, N. M. McClure-Griffiths, S. P. Ellingsen, J. A. Green, J. F. Gómez, V. Krishnan, J. M. Dickey, H. Imai, S. J. Gibson, P. Hennebelle, N. LoT. Hayakawa, Y. Fukui, A. Mizuno

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

42 Citations (Scopus)
28 Downloads (Pure)


The 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-MHzmain 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.

Original languageEnglish
Pages (from-to)1596-1614
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Publication statusPublished - Apr 2014
Externally publishedYes

Bibliographical note

Copyright 2014 The Authors. First published in Monthly Notices of the Royal Astronomical Society, 439(2), 1596-1614. The original publication is available at http://doi.org/10.1093/mnras/stu032, published by Oxford University Press on behalf of the Royal Astronomical Society. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.


Dive into the research topics of 'SPLASH: the Southern Parkes Large-Area Survey in Hydroxyl - first science from the pilot region'. Together they form a unique fingerprint.

Cite this