- evn2024@mpifr.de
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Contribution
VLBI monitoring of the structure of the ICRF sources − The Bordeaux VLBI Image Database
Speakers
- Dr. Patrick CHARLOT
Primary authors
- Mr. Arnaud COLLIOUD (Laboratoire d'Astrophysique de Bordeaux, University of Bordeaux)
Co-authors
- Dr. Patrick CHARLOT (Laboratoire d'Astrophysique de Bordeaux, University of Bordeaux)
Content
The extragalactic radio sources that make up the International Celestial Reference Frame (ICRF) can exhibit extended and time-variable brightness distributions (or structures) on VLBI scales, setting limits on the accuracy of the astrometric source positions determined from the VLBI measurements. For this reason, the International VLBI Service for Geodesy and Astrometry (IVS) has organized regular VLBI observations, the so-called “Research & Development with the VLBA” (RDV) sessions, for more than two decades to monitor these structures. The RDV sessions are conducted six times a year using a network of 14 to 20 radio telescopes (including the VLBA plus several IVS antennas) for a duration of 24 hours at S/X band (2/8 GHz). We carry out systematic imaging of the sources observed in these sessions with the goal of tracking the structural evolution of the ICRF sources on the long-term. The VLBI images produced along with metrics that characterize the source structure (compactness, structure index, flux density) are made available to the scientific community via the Bordeaux VLBI Image Database (BVID). Occasionally, other sessions, either at higher radio frequencies, i.e. K band (24 GHz) and Q band (43 GHz), or from other observing programs, are also used for imaging, the results of which are made available to the community similarly through the BVID. At present, the database includes more than 8000 VLBI images for more than 1500 sources, with up to 50+ epochs per source. The available data may be used for astrometric and astrophysical research, like selecting the defining sources for the ICRF, modeling source structure in astrometric and geodetic VLBI, and studying the nature and evolution of the sources. The BVID is accessible at the following url: https://bvid.astrophy.u-bordeaux.fr.