Radio circular polarization produced in helical magnetic fields in eight active galactic nuclei

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dc.contributor.author Gabuzda, Denise
dc.contributor.author Vitrishchak, V. M.
dc.contributor.author Mahmud, M.
dc.contributor.author O'Sullivan, Shane P.
dc.date.accessioned 2017-11-07T09:38:57Z
dc.date.available 2017-11-07T09:38:57Z
dc.date.issued 2008
dc.identifier.citation Gabuzda, D. C., Vitrishchak, V. M., Mahmud, M. and O'Sullivan, S. P. (2008) 'Radio circular polarization produced in helical magnetic fields in eight active galactic nuclei', Monthly Notices of the Royal Astronomical Society, 384(3), pp. 1003-1014. doi: 10.1111/j.1365-2966.2007.12773.x en
dc.identifier.volume 384
dc.identifier.issued 3
dc.identifier.startpage 1003
dc.identifier.endpage 1014
dc.identifier.issn 0035-8711
dc.identifier.uri http://hdl.handle.net/10468/4976
dc.identifier.doi 10.1111/j.1365-2966.2007.12773.x
dc.description.abstract Homan & Lister have recently published circular polarization (CP) detections for 34 objects in the MOJAVE sample - a set of bright, compact active galactic nuclei (AGN) being monitored by the Very Long Baseline Array at 15 GHz. We report the detection of 15-GHz parsec-scale CP in two more AGN (3C 345 and 2231+114), and confirm the MOJAVE detection of CP in 1633+382. It is generally believed that the most likely mechanism for the generation of this CP is Faraday conversion of linear polarization (LP) to CP. A helical jet magnetic field (B field) geometry can facilitate this process-linearly polarized emission from the far side of the jet is converted to CP as it passes through the magnetized plasma at the front side of the jet on its way towards the observer. In this case, the sign of the generated CP is essentially determined by the pitch angle and helicity of the helical B field. We have determined the pitch-angle regimes and helicities of the helical jet B fields in eight AGN for which parsec-scale CP has been detected, and used them to predict the expected CP signs for these AGN if the CP is generated via conversion in these helical fields. We have obtained the intriguing result that our predictions agree with the observed signs in all eight cases, provided that the longitudinal B field components in the jets correspond to south magnetic poles. This clearly non-random pattern demonstrates that the observed CP in AGN is directly associated with the presence of helical jet B fields. These results suggest that helical B fields are ubiquitous in AGN jets. en
dc.format.mimetype application/pdf en
dc.language.iso en en
dc.publisher Oxford University Press en
dc.relation.uri https://academic.oup.com/mnras/article-lookup/doi/10.1111/j.1365-2966.2007.12773.x
dc.rights © 2008, the Authors. Journal compilation © 2008, RAS en
dc.subject Active en
dc.subject Galaxies en
dc.subject Jets en
dc.subject Quasars en
dc.subject General en
dc.title Radio circular polarization produced in helical magnetic fields in eight active galactic nuclei en
dc.type Article (peer-reviewed) en
dc.internal.authorcontactother Denise Gabuzda, Physics, University College Cork, Cork, Ireland. +353-21-490-3000 Email: d.gabuzda@ucc.ie en
dc.internal.availability Full text available en
dc.description.version Published Version en
dc.description.status Peer reviewed en
dc.identifier.journaltitle Monthly Notices of the Royal Astronomical Society en
dc.internal.IRISemailaddress d.gabuzda@ucc.ie en


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