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

TL;DR

This paper discusses a VLBI survey aimed at identifying weak radio sources to improve the alignment between the optical GAIA frame and the radio ICRF, enhancing celestial reference frame accuracy.

Contribution

It introduces a new VLBI survey targeting weaker radio sources to increase the number of suitable reference points for frame alignment.

Findings

Preliminary observations of 224 sources conducted.

The survey targets sources 20 times weaker than current ICRF sources.

Initial results suggest potential for improved frame alignment.

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. 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.