Aligning VLBI images of active galactic nuclei at different frequencies

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dc.contributor.authorCroke, S. M.
dc.contributor.authorGabuzda, Denise
dc.date.accessioned2017-11-07T09:38:57Z
dc.date.available2017-11-07T09:38:57Z
dc.date.issued2008
dc.description.abstractMany important techniques for investigating the properties of extragalactic radio sources, such as spectral-index and rotation-measure mapping, involve the comparison of images at two or more frequencies. In the case of radio interferometric data, this can be done by comparing the CLEAN maps obtained at the different frequencies. However, intrinsic differences in images due to the frequency dependence of the radio emission can be distorted by additional differences that arise due to source variability (if the data to be compared are obtained at different times), image misalignment, and the frequency dependence of the sensitivity to weak emission and the angular resolution provided by the observations (the resolution of an interferometer depends on the lengths of its baselines in units of the observing wavelength). These effects must be corrected for as best as possible before multifrequency data comparison techniques can be applied. We consider the origins for the aforementioned factors, outline the standard techniques used to overcome these difficulties, and describe in detail a technique developed by us, based on the cross-correlation technique widely used in other fields, to correct for misalignments between maps at different frequencies.en
dc.description.statusPeer revieweden
dc.description.versionPublished Versionen
dc.format.mimetypeapplication/pdfen
dc.identifier.citationCroke, S. M. and Gabuzda, D. C. (2008) 'Aligning VLBI images of active galactic nuclei at different frequencies', Monthly Notices of the Royal Astronomical Society, 386(2), pp. 619-626. doi: 10.1111/j.1365-2966.2008.13087.xen
dc.identifier.doi10.1111/j.1365-2966.2008.13087.x
dc.identifier.endpage626
dc.identifier.issn0035-8711
dc.identifier.issued2
dc.identifier.journaltitleMonthly Notices of the Royal Astronomical Societyen
dc.identifier.startpage619
dc.identifier.urihttps://hdl.handle.net/10468/4975
dc.identifier.volume386
dc.language.isoenen
dc.publisherOxford University Pressen
dc.relation.urihttps://academic.oup.com/mnras/article-lookup/doi/10.1111/j.1365-2966.2008.13087.x
dc.rights© 2008, the Authors. Journal compilation © 2008, RASen
dc.subjectTechniquesen
dc.subjectImage processingen
dc.subjectGalaxiesen
dc.subjectActiveen
dc.titleAligning VLBI images of active galactic nuclei at different frequenciesen
dc.typeArticle (peer-reviewed)en
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