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Radio source calibration for the Very Small Array and other cosmic microwave background instruments at around 30 GHz |
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| Authors: | Yaser A Hafez Rod D Davies Richard J Davis Clive Dickinson Elia S Battistelli Francisco Blanco Kieran Cleary Thomas Franzen Ricardo Genova-Santos Keith Grainge Michael P Hobson Michael E Jones Katy Lancaster Anthony N Lasenby Carmen P Padilla-Torres José Alberto Rubiño-Martin Rafael Rebolo Richard D E Saunders Paul F Scott Angela C Taylor David Titterington Marco Tucci Robert A Watson |
| Institution: | National Centre for Mathematics and Physics, KACST, PO Box 6086, Riyadh 11442, Saudi Arabia;Jodrell Bank Centre for Astrophysics, The University of Manchester, Manchester M13 9PL;Infrared Processing and Analysis Center, California Institute of Technology, M/S 220-6, 1200 E. California Blvd., Pasadena, CA 91125, USA;Instituto de Astrofisíca de Canarias, 38200 La Laguna, Tenerife, Canary Islands, Spain;Department of Physics &Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, British Columbia, Canada V6T 1Z1;California Institute of Technology, M/S 105-24, 1200 E. California Blvd., Pasadena, CA 91125, USA;Astrophysics Group, Cavendish Laboratory, University of Cambridge, Madingley Road, Cambridge CB3 0HE;Astrophysics Group, Denys Wilkinson Building, University of Oxford, Keeble Road, Oxford OX1 3RH;H. H. Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL |
| Abstract: | Accurate calibration of data is essential for the current generation of cosmic microwave background (CMB) experiments. Using data from the Very Small Array (VSA), we describe procedures which will lead to an accuracy of 1 per cent or better for experiments such as the VSA and CBI. Particular attention is paid to the stability of the receiver systems, the quality of the site and frequent observations of reference sources. At 30 GHz the careful correction for atmospheric emission and absorption is shown to be essential for achieving 1 per cent precision. The sources for which a 1 per cent relative flux density calibration was achieved included Cas A, Cyg A, Tau A and NGC 7027 and the planets Venus, Jupiter and Saturn. A flux density, or brightness temperature in the case of the planets, was derived at 33 GHz relative to Jupiter which was adopted as the fundamental calibrator. A spectral index at ∼30 GHz is given for each. Cas A, Tau A, NGC 7027 and Venus were examined for variability. Cas A was found to be decreasing at 0.394 ± 0.019 per cent yr |
| Keywords: | methods: observational techniques: interferometric cosmic microwave background cosmology: observations radio continuum: ISM radio continuum: Solar system |