Evidence for toroidal B-field components in AGN jets on kiloparsec scales

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dc.contributor.authorKnuettel, Sebastian
dc.contributor.authorGabuzda, Denise
dc.contributor.authorO'Sullivan, Shane
dc.contributor.funderIrish Research Council
dc.date.accessioned2017-12-08T13:33:48Z
dc.date.available2017-12-08T13:33:48Z
dc.date.issued2017-10-04
dc.description.abstractThough helical magnetic fields are generally believed to arise when the jets of Active Galactic Nuclei (AGN) are launched, it is still unclear what role they play (and if they survive) to the largest jet scales. A helical or toroidal B-field may contribute substantially to the collimation of the jet. This B-field structure can be detected in images of the Faraday rotation measure (RM)—a measure of the change in polarisation angle of an electromagnetic wave as it passes through a magneto-ionic medium. The Faraday rotation measure is directly proportional to the line-of-sight magnetic field; therefore a monotonic gradient in the RM transverse to the jet indicates similar behaviour of the line-of-sight B-field component. This type of analysis has mostly been done on parsec scales using VLBI observations at centimetre wavelengths, while relatively few studies have probed decaparsec to kiloparsec scales. The detection of RM gradients with significances of 3σ or more on such large scales can demonstrate the presence of a toroidal field component, which may be associated with a helical field that has persisted to these distances from the centre of the AGN. We present the results of new Faraday rotation analyses for 2 AGN on kiloparsec scales based on multiwavelength VLA observations, with robust transverse RM gradients detected in both. Furthermore, the direction of the inferred toroidal B-fields on the sky supports previous results indicating a predominance of outward currents in the jets on kiloparsec scales.en
dc.description.sponsorshipIrish Research Council (Government of Ireland Postgraduate Scholarship)en
dc.description.statusPeer revieweden
dc.description.versionPublished Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.articleid61
dc.identifier.citationKnuettel, S., Gabuzda, D. and O’Sullivan, S. (2017) 'Evidence for toroidal B-field components in AGN jets on kiloparsec scales', Galaxies, 5(4), 61 (6pp). doi: 10.3390/galaxies5040061en
dc.identifier.doi10.3390/galaxies5040061
dc.identifier.endpage6
dc.identifier.issn2075-4434
dc.identifier.issued4
dc.identifier.journaltitleGalaxiesen
dc.identifier.startpage1
dc.identifier.urihttps://hdl.handle.net/10468/5154
dc.identifier.volume5
dc.language.isoenen
dc.publisherMDPIen
dc.relation.urihttp://www.mdpi.com/2075-4434/5/4/61
dc.rights© 2017, the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).en
dc.rights.urihttps://creativecommons.org/licenses/by/4.0/
dc.subjectActive galactic nucleien
dc.subjectMagnetic fieldsen
dc.subjectRadio interferometryen
dc.titleEvidence for toroidal B-field components in AGN jets on kiloparsec scalesen
dc.typeArticle (peer-reviewed)en
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