CHARLOT, P.; FEY, A. L.; OJHA, R.; BOBOLTZ, D. A.

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CHARLOT, P.
Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux [L3AB]
Observatoire aquitain des sciences de l'univers [OASU]
Laboratoire d'Astrophysique de Bordeaux [Pessac] [LAB]

FEY, A. L.
U.S. Naval Observatory

OJHA, R.
U.S. Naval Observatory

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Communication dans un congrès

Ce document a été publié dans

International VLBI Service for Geodesy and Astrometry 2006 General Meeting Proceedings}, Concepción, Chili, 9-11 January 2006, Eds. D. Behrend and K. D. Baver, NASA/CP-2006-214140,, International VLBI Service for Geodesy and Astrometry 2006 General Meeting Proceedings}, Concepción, Chili, 9-11 January 2006, Eds. D. Behrend and K. D. Baver, NASA/CP-2006-214140,, International VLBI Service for Geodesy and Astrometry 2006, 2006, Concepción. 2006 n° 321-325, p. Proceedings edited by Dirk Behrend and Karen Baver, 2006, NASA/CP-2006-214140, p. 321

Résumé en anglais

The intrinsic radio structure of the extragalactic sources is one of the limiting errors in the analysis of astrometric and geodetic VLBI observations. Based on VLBI images obtained with the VLBA and other VLBI telescopes around the world, we evaluate this effect for 557 sources (78% of the ICRF) and calculate a so-called ``structure index" to define the astrometric source quality. The structure index ranges from 1 for the most compact sources to 4 for the most extended sources. The most recent addition to our data base is for a hundred southern hemisphere sources. We discuss the overall distribution of structure index in the ICRF and the structure index variability with time for those sources that have VLBI images available at multiple epochs. Based on these data, we identify a set of 239 sources that have good or excellent astrometric suitability. We also suggest that the structure index indicator be used as a primary criterion to select defining sources for the next ICRF realization.< Réduire

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Unités de recherche

Laboratoire d'Astrophysique de Bordeaux (LAB) - UMR 5804