A Vlbi Survey of Weak Extragalactic Radio Sources for the Alignment of the Icrf and the Future Gaia Frame

TL;DR

This paper reports on a VLBI survey targeting weak extragalactic radio sources to improve the alignment between the optical Gaia frame and the radio ICRF, aiming for higher astrometric accuracy.

Contribution

It introduces a new VLBI survey of 450 faint radio sources to enhance the alignment between Gaia and ICRF frames, addressing current limitations.

Findings

Observed 224 sources with the European VLBI Network.

Identified additional high-quality radio sources for frame alignment.

Preliminary results show potential for improved frame linkage.

Abstract

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. The paper presents the observing strategy and includes preliminary results of observation of 224 of these sources with the European VLBI Network in June 2007.