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New H_(2)O masers in Seyfert and FIR bright galaxies: III. The southern sample

Surcis, G. and Tarchi, A. and Ott, J. and Lovell, J. and Castangia, P. (2009) New H_(2)O masers in Seyfert and FIR bright galaxies: III. The southern sample. Astronomy and Astrophysics, 502 (2). pp. 529-540. ISSN 0004-6361.

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Context. A relationship between the water maser detection rate and far infrared (FIR) flux densities was established as a result of two 22 GHz maser surveys in a complete sample of galaxies (Dec > −30°) with flux densities of >50 Jy and >30 Jy. Aims. We attempted to discover new maser sources and investigate the galaxies hosting the maser spots by extending previous surveys to southern galaxies with particular emphasis on the study of their nuclear regions. Methods. A sample of 12 galaxies with Dec < −30° and S_(100 μm) > 50 Jy was observed with the 70-m telescope of the Canberra deep space communication complex (CDSCC) at Tidbinbilla (Australia) in a search for water maser emission. The average 3σ noise level of the survey was 15 mJy for a 0.42 km s^(−1) channel, corresponding to a detection threshold of ∼0.1 L_☉ for the isotropic maser luminosity at a distance of 25 Mpc. Results. Two new detections are reported: a kilomaser with an isotropic luminosity L_(H_(2)O) ~ 5 L_☉ in NGC 3620 and a maser with about twice this luminosity in the merger system NGC 3256. The detections have been followed-up by continuum and spectral line interferometric observations with the Australia Telescope Compact Array (ATCA). In NGC 3256, a fraction (about a third) of the maser emission originates in two hot spots associated with star formation activity, which are offset from the galactic nuclei of the system. The remaining emission may originate in weaker centres of maser activity distributed over the central 50". For NGC 3620, the water maser is coincident with the nuclear region of the galaxy. Our continuum observations indicate that the nature of the nuclear emission is probably linked to particularly intense star formation. Including the historical detection in NGC 4945, the water maser detection rate in the southern sample is 15% (3/20), consistent with the northern sample. The high rate of maser detections in the complete all-sky FIR sample (23%, 15/65) confirms the existence of a link between overall FIR flux density and maser phenomena. A relation between H_(2)O and OH masers in the FIR sample is also discussed.

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Ott, J.0000-0001-8224-1956
Additional Information:© 2009 EDP Sciences. Received 20 January 2009; accepted 30 April 2009. We wish to thank Shinji Horiuchi for performing part of the observations at Tidbinbilla and for useful discussions, and an anonymous referee for making useful suggestions. A.T. would like to thank Lincoln Greenhill and Paul Kondratko for helpful suggestions in the early stages of this project, and Alessandro Riggio for his advice on statistics. G.S. would like to thank Wouter Vlemmings for helpful comments. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, Caltech, under contract with NASA. This research has also made use of NASA’s Astrophysics Data System Abstract Service (ADS). The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. G.S. is aMember of the International Max Planck Research School (IMPRS) for Radio and Infrared Astronomy at the Universities of Bonn and Cologne.
Subject Keywords:galaxies: individual: NGC 3620, NGC 3256; galaxies: active; galaxies: ISM; masers; radio lines: ISM; radio lines: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20090828-112247036
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Official Citation:New H_(2)O masers in Seyfert and FIR bright galaxies - III. The southern sample G. Surcis, A. Tarchi, C. Henkel, J. Ott, J. Lovell and P. Castangia A&A 502 (2) 529-540 (2009) DOI: 10.1051/0004-6361/200911685
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:15407
Deposited By: Jason Perez
Deposited On:03 Sep 2009 18:02
Last Modified:03 Oct 2019 00:57

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