4064 10 archive 337 disk0/00/00/40/64 2008-04-07 14:20:44 2008-09-01 01:51:55 2008-07-16 17:04:48 article show Simon.Ellingsen@utas.edu.au McCallum JN Ellingsen SP Simon.Ellingsen@utas.edu.au Lovell JEJ pub 240101 970102 780102 restricted masers – polarization – scattering – galaxies: individual: Circinus. The definitive version is available at www.blackwell-synergy.com category => A1 categoryDesc => Refereed Article in a Scholarly Journal eprintID => 0 field1 => Monthly Notices of the Royal Astronomical Society field10 => field11 => field12 => field13 => field2 => "Oxford, England" field3 => 376 field4 => 2 field5 => 549-556 field6 => Blackwell Publishing field7 => 0035-8711 field8 => field9 => funding => Q grant => E0012810 lastUpdate => 5/02/2008 rfcd => 240101 seo => 780102 themeArea => FT title => Magnetic field limits and spectral variability in the Circinus galaxy H2O megamasers tor => PB uid => 44267 update => no We have used the Australia Telescope Compact Array (ATCA) to search for polarized emission from the Circinus galaxy H2O megamasers. No linear or circular polarized emission was detected with 3σ upper limits of 24 and 39 mJy, respectively, corresponding to fractional polarizations of 0.6 and 0.9 per cent for the strongest line. These results allow us to place upper limits on the strength of the nuclear magnetic field of 150 mG near the outer edge of the masing disc and 360 mG at the inner edge. Rapid variability, thought to be due to interstellar scintillation, is a well-known feature of the Circinus H2O megamasers. Our Stokes-I data show evidence for changes in the shape of the maser line spectral profiles, as well as their intensity. In addition to the rapid variations, the maser light curves also exhibit variations with a time-scale of the order of days (although our observations are too short to characterize this well). These behaviours support the hypothesis that the Circinus H2O megamasers undergo diffractive interstellar scintillation, which has previously only been observed in pulsars and in one active galactic nucleus. 2007 published Monthly Notices of the Royal Astronomical Society 376 2 Blackwell Publishing 549-556 10.1111/j.1365-2966.2007.11492.x TRUE 0035-8711 http://dx.doi.org/10.1111/j.1365-2966.2007.11492.x 6463 3 4064 1 application/pdf en staffonly

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