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    Green bank telescope observations of the water masers of NGC 3079: Accretion disk magnetic field and maser scintillation

    Access Status
    Open access via publisher
    Authors
    Vlemmings, Wouter
    Bignall, Hayley
    Diamond, Phil
    Date
    2007
    Type
    Journal Article
    
    Metadata
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    Citation
    Vlemmings, W.H.T. and Bignall, H.E. and Diamond, P.J. 2007. Green bank telescope observations of the water masers of NGC 3079: Accretion disk magnetic field and maser scintillation. The Astrophysical Journal 656 (1): pp. 198-205.
    Source Title
    The Astrophysical Journal
    DOI
    10.1086/510515
    ISSN
    0004637X
    URI
    http://hdl.handle.net/20.500.11937/27844
    Collection
    • Curtin Research Publications
    Abstract

    We present observations of the 22 GHz H2O megamasers in the circumnuclear disk of NGC 3079 obtained with the Green Bank Telescope. The data are analyzed for circular polarization due to the Zeeman-induced splitting of the H2O maser lines. No circular polarization is detected, and we derive a 1 upper limit of 11 mG for the toroidal magnetic field at 0.64 pc from the central black hole. This is the tightest upper limit for the magnetic field around a black hole to date. We use the magnetic field limit to derive an estimate of the mass accretion onto the central black hole. In addition to the polarimetric results, we present an observation of rapid variability in the maser lines, which we explain as weak interstellar scintillation. From the scintillation parameters, we estimate an intrinsic size of the mostly saturated maser features of 12 as. This is consistent with models assuming a thick, clumpy accretion disk.

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