Search for correlations between the optical and radio polarization of active galactic nuclei - II. VLBA polarization data at 12+15+22+24+43 GHz

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dc.contributor.author Algaba, Juan Carlos
dc.contributor.author Gabuzda, Denise
dc.contributor.author Smith, P. S.
dc.date.accessioned 2017-11-07T09:38:54Z
dc.date.available 2017-11-07T09:38:54Z
dc.date.issued 2012
dc.identifier.citation Algaba, J. C., Gabuzda, D. C. and Smith, P. S. (2012) 'Search for correlations between the optical and radio polarization of active galactic nuclei – II. VLBA polarization data at 12+15+22+24+43 GHz', Monthly Notices of the Royal Astronomical Society, 420(1), pp. 542-553. doi: 10.1111/j.1365-2966.2011.20061.x en
dc.identifier.volume 420
dc.identifier.issued 1
dc.identifier.startpage 542
dc.identifier.endpage 553
dc.identifier.issn 0035-8711
dc.identifier.uri http://hdl.handle.net/10468/4961
dc.identifier.doi 10.1111/j.1365-2966.2011.20061.x
dc.description.abstract Previous research showed that most BL Lac objects and some quasars have aligned very long baseline interferometry (VLBI) core and optical polarizations, although some of the active galactic nuclei (AGNs) also showed no obvious relationship between their VLBI core and optical polarization angles. This may indicate that some AGNs have cospatial regions of optical and radio emission, while others do not. However, another possibility is that some of the VLBI cores had Faraday rotations of the order of several tens of thousands of rad m(-2), which were not properly fitted using the three-frequency data due to n pi ambiguities in the observed polarization angles, leading to incorrect subtraction of the effects of the core Faraday rotation, and so incorrect intrinsic radio polarization angles chi(0). With this is mind, we obtained additional 12+15+22+24+43 GHz plus optical observations for eight of 40 AGNs previously considered, enabling improved sampling of Faraday effects. Our results indicate that, although some VLBI radio cores have comparatively high rotation measures, this alone cannot explain the misalignments found between the radio core and optical VLBI polarization angles, Delta chi = vertical bar chi(opt) - chi(0)|. Comparisons between Delta chi and (i) the orientation of chi(0) relative to the jet direction, (ii) the degree of polarization of the core, (iii) a depolarization factor, (iv) the core rotation measures and (v) the core magnetic fields 1 pc from the jet base do not yield evidence for any correlations between these properties. There is, however, some evidence that the maximum observed Delta chi tends to decrease as the core-region magnetic field increases, suggesting that large misalignments in Delta chi could be associated in part with relatively low core magnetic fields. Thus, although the overall distribution of Delta chi for all 40 sources in our sample does show a significant peak at Delta chi similar to 0, it remains unclear what distinguishes these AGN cores from those showing appreciable misalignment between optical and VLBI core polarization position angles. en
dc.description.sponsorship National Aeronautics and Space Administration (Spitzer)/Jet Propulsion Laboratory/Spitzer (1256424); National Aeronautics and Space Administration (NNX08AW56G, NNX09AU10G) 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.1365-2966.2011.20061.x
dc.rights © 2011, the Authors. Monthly Notices of the Royal Astronomical Society © 2011, RAS en
dc.subject Polarization en
dc.subject Galaxies en
dc.subject Active en
dc.subject Nuclei en
dc.subject Radio continuum en
dc.title Search for correlations between the optical and radio polarization of active galactic nuclei - II. VLBA polarization data at 12+15+22+24+43 GHz 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.contributor.funder Jet Propulsion Laboratory
dc.contributor.funder National Aeronautics and Space Administration
dc.contributor.funder Science Foundation Ireland
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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