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Patrick Charlot
Type of contribution: oral

Reducing the impact of source structure on the celestial frame: modeling or mitigation strategies?

Patrick Charlot, Laboratoire d'Astrophysique de Bordeaux Arnaud Collioud, Laboratoire d'Astrophysique de Bordeaux

As the accuracy of VLBI observations increases, source structure is expected to become an ever-growing limitation in further improving the quality of the celestial reference frame. Very few sources are found to be fully point-like on VLBI scales, requiring modeling or mitigation strategies to reduce the effects caused by such structures. Incorporating structure modeling in the astrometric and geodetic VLBI data analysis requires availability of VLBI images on a recurrent basis since the source morphology often varies with time. Additionally, one should have the ability to properly align these images over time and frequency since these have no absolute sky coordinates due to the self-calibration procedure used to produce such images. Alternately, one may develop mitigation strategies to reduce the effects of such structures in the determination of the celestial frame. A possibility is to use the so-called structure indices, now available for more than 1000 sources from the Bordeaux VLBI Image Database (BVID), as a filter for scheduling only the most suitable sources at a given epoch. Such a filter is also worthwhile to properly select defining sources when a new realization of the celestial frame is built. This paper reviews all source structure material available to deal with the issue as best as we can in the framework of the upcoming ICRF3 realization.