Three-dimensional magnetic field structure of six parsec-scale active galactic nuclei jets

Show simple item record O'Sullivan, Shane P. Gabuzda, Denise 2017-11-07T09:38:56Z 2017-11-07T09:38:56Z 2009
dc.identifier.citation O'Sullivan, S. P. and Gabuzda, D. C. (2009) 'Three-dimensional magnetic field structure of six parsec-scale active galactic nuclei jets', Monthly Notices of the Royal Astronomical Society, 393(2), pp. 429-456. doi: 10.1111/j.1365-2966.2008.14213.x en
dc.identifier.volume 393
dc.identifier.issued 2
dc.identifier.startpage 429
dc.identifier.endpage 456
dc.identifier.issn 0035-8711
dc.identifier.doi 10.1111/j.1365-2966.2008.14213.x
dc.description.abstract The parsec-scale Faraday rotation measure (RM) distribution of six 'blazars' (0954+658, 1156+295, 1418+546, 1749+096, 2007+777 and 2200+420) are investigated using multi-frequency (4.6, 5.1, 7.9, 8.9, 12.9, 15.4, 22 and 43 GHz) polarization observations with the American Very Long Baseline Array taken on 2006 July 2. Analysis of the RM provides the direction of the line-of-sight (LoS) magnetic field component, as well as the intrinsic (unrotated) two-dimensional polarization distribution on the plane of the sky. Our results show that the magnitude of the core RM increases systematically with frequency, and is well described by a power law, where |RM(core)| proportional to nu(a). Our measured values of a vary from 0.9 to 3.8, providing information on the assumed power-law fall-off in the electron density ( ne) with distance from the central engine (r) for each source. RM gradients were detected across the jets of 0954+658, 1156+295 and 1418+546, supporting the presence of helical magnetic fields in a sheath or boundary layer surrounding their jets. We find a bi-modal distribution of the intrinsic jet polarization orientation, with the polarization angles either aligned or orthogonal to the jet direction. The polarization of 2200+420 displays a continuous structure, with the polarization angles remaining aligned with the jet direction even as it bends. This indicates that the magnetic field structure in the synchrotron emitting plasma is dominated by an ordered transverse component. A helical magnetic field geometry can neatly explain both the bi-model distribution of the jet polarization orientation and the ordered polarization structure on these scales. For 0954+658, 1418+546 and 2200+420, we find that the core RM changes sign with distance from the central engine. We provide an explanation for this by considering a boundary layer of Faraday rotating material threaded by a helical magnetic field, where bends in the relativistic jet or accelerating/decelerating flows give rise to changes in the dominant LoS components of the magnetic field, which in turn gives rise to different signs of the RM. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Oxford University Press en
dc.rights © 2009, the Authors. Journal compilation © 2009, RAS en
dc.subject Jets en
dc.subject Magnetic fields en
dc.subject Radio continuum en
dc.subject Galaxies en
dc.title Three-dimensional magnetic field structure of six parsec-scale active galactic nuclei jets en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Shane O'Sullivan, Physics, University College Cork, Cork, Ireland. +353-21-490-3000 en
dc.internal.availability Full text available en
dc.description.version Published Version en
dc.contributor.funder University of Michigan
dc.contributor.funder National Science Foundation
dc.contributor.funder Irish Research Council for Science, Engineering and Technology
dc.description.status Peer reviewed en
dc.identifier.journaltitle Monthly Notices of the Royal Astronomical Society en
dc.internal.IRISemailaddress en

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