Aligning VLBI images of active galactic nuclei at different frequencies

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dc.contributor.author Croke, S. M.
dc.contributor.author Gabuzda, Denise
dc.date.accessioned 2017-11-07T09:38:57Z
dc.date.available 2017-11-07T09:38:57Z
dc.date.issued 2008
dc.identifier.citation Croke, 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.x en
dc.identifier.volume 386
dc.identifier.issued 2
dc.identifier.startpage 619
dc.identifier.endpage 626
dc.identifier.issn 0035-8711
dc.identifier.uri http://hdl.handle.net/10468/4975
dc.identifier.doi 10.1111/j.1365-2966.2008.13087.x
dc.description.abstract Many 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.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.1365-2966.2008.13087.x
dc.rights © 2008, the Authors. Journal compilation © 2008, RAS en
dc.subject Techniques en
dc.subject Image processing en
dc.subject Galaxies en
dc.subject Active en
dc.title Aligning VLBI images of active galactic nuclei at different frequencies 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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