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VLBI observations of weak extragalactic radio sources for the alignment of the future Gaia frame with the ICRF

Published online by Cambridge University Press:  01 October 2007

G. Bourda ,
P. Charlot ,
R. Porcas  and
S. Garrington
G. Bourda
Affiliation:
Laboratoire d'Astrophysique de Bordeaux, Université Bordeaux 1, CNRS, Floirac, France email: bourda@obs.u-bordeaux1.fr
P. Charlot
Affiliation:
Laboratoire d'Astrophysique de Bordeaux, Université Bordeaux 1, CNRS, Floirac, France email: bourda@obs.u-bordeaux1.fr
R. Porcas
Affiliation:
Max Planck Institute for Radio Astronomy, Bonn, Germany
S. Garrington
Affiliation:
Jodrell Bank Observatory, The University of Manchester, Macclesfield, UK
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Abstract

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The space astrometry mission Gaia will construct a dense optical QSO-based celestial reference frame. For consistency between the optical and radio positions, it will be important to align the Gaia frame and the International Celestial Reference Frame (ICRF) with the highest accuracy. Currently, it is found that only 10% of the ICRF sources are suitable to establish this link, either because they are not bright enough at optical wavelengths or because they have significant extended radio emission which precludes reaching the highest astrometric accuracy. In order to improve the situation, we have initiated a VLBI survey dedicated to finding additional high-quality radio sources for aligning the two frames. The sample consists of about 450 sources, typically 20 times weaker than the current ICRF sources, which have been selected by cross-correlating optical and radio catalogues. This paper presents the observing strategy and includes preliminary results of observation of 224 of these sources with the European VLBI Network in June 2007.

Keywords

astrometryreference systemsquasars: general
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S248: A Giant Step: from Milli- to Micro-arcsecond Astrometry , October 2007 , pp. 324 - 325
Copyright
Copyright © International Astronomical Union 2008

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