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Radio source calibration for the Very Small Array and other cosmic microwave background instruments at around 30 GHz

Hafez, Yaser A. and Davies, Rod D. and Davis, Richard J. and Dickinson, Clive and Battistelli, Elia S. and Blanco, Francisco and Cleary, Kieran and Franzen, Thomas and Genova-Santos, Ricardo and Grainge, Keith and Hobson, Michael P. and Jones, Michael E. and Lancaster, Katy and Lasenby, Anthony N. and Padilla-Torres, Carmen P. and Rubiño-Martin, José Alberto and Rebolo, Rafael and Saunders, Richard D. E. and Scott, Paul F. and Taylor, Angela C. and Titterington, David and Tucci, Marco and Watson, Robert A. (2008) Radio source calibration for the Very Small Array and other cosmic microwave background instruments at around 30 GHz. Monthly Notices of the Royal Astronomical Society, 388 (4). pp. 1775-1786. ISSN 0035-8711. https://resolver.caltech.edu/CaltechAUTHORS:HAFmnras08

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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 similar to 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^(-1) over the period 2001 March to 2004 August. In the same period Tau A was decreasing at 0.22 ± 0.07 per cent yr^(-1). A survey of the published data showed that the planetary nebula NGC 7027 decreased at 0.16 ± 0.04 per cent yr^(-1) over the period 1967-2003. Venus showed an insignificant (1.5 ±1.3 per cent) variation with Venusian illumination. The integrated polarization of Tau A at 33 GHz was found to be 7.8 ± 0.6 per cent at position angle =148° ± 3°.


Item Type:Article
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http://dx.doi.org/10.1111/j.1365-2966.2008.13515.xDOIUNSPECIFIED
Additional Information:© 2008 The Authors. Journal compilation © 2008 RAS. Accepted 2008 May 26. Received 2008 May 23; in original form 2008 April 18. Published Online: 11 July 2008. We thank the referee, Dayton Jones, for a careful reading of the paper which has led to a number of improvements. YAH thanks the King Abdulaziz City of Science and Technology for support. YAH also thanks His Highness Prince Dr Turki Bin Saud Bin Mohammad Al Saud, the vice president of KACST for the Research institutes, for his personal support. CD acknowledges support from the US Planck Project, which is funded by the NASA Science Mission Directorate.
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Funding AgencyGrant Number
King Abdulaziz City of Science and TechnologyUNSPECIFIED
NASAUNSPECIFIED
Subject Keywords:methods: observational; techniques: interferometric; cosmic microwave background; cosmology: observations; radio continuum: ISM; radio continuum: Solar system
Issue or Number:4
Record Number:CaltechAUTHORS:HAFmnras08
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:HAFmnras08
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12400
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:15 Jan 2009 21:49
Last Modified:03 Oct 2019 00:28

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