Croke, Sarah 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. ISSN 0035-8711Full text not available in this repository. (Request a copy from the Strathclyde author)
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.
|Keywords:||techniques, image processing, galaxies, active, Physics, Astronomy and Astrophysics, Space and Planetary Science|
|Subjects:||Science > Physics|
|Department:||Faculty of Science > Physics|
|Depositing user:||Strathprints Administrator|
|Date Deposited:||04 Jun 2010 15:49|
|Last modified:||05 May 2016 00:05|