The catalogue of positions of optically bright extragalactic radio sources OBRS-1

TL;DR

This paper presents a catalog of 105 extragalactic radio sources with milliarcsecond positional accuracy, supporting the comparison of optical and radio coordinate systems crucial for validating space-based astrometry.

Contribution

It provides the first detailed catalog of positions for these sources, enhancing the robustness of radio-optical coordinate system comparisons.

Findings

Median positional accuracy of 1.1 mas

Coordinates range from 0.3 to 7 mas

Supports validation of astrometric techniques

Abstract

It is expected that the European Space Agency mission Gaia will make possible to determine coordinates in the optical domain of more than 500000 quasars. In 2006, a radio astrometry project was launched with the overall goal to make comparison of coordinate systems derived from future space-born astrometry instruments with the coordinate system constructed from analysis of the global very long baseline interferometry (VLBI) more robust. Investigation of their rotation, zonal errors, and the non-alignment of the radio and optical positions caused by both radio and optical structures are important for validation of both techniques. In order to support these studies, the densification of the list of compact extragalactic objects that are bright in both radio and optical ranges is desirable. A set of 105 objects from the list of 398 compact extragalactic radio sources with declination > -10 deg was observed with the VLBA+EVN with the primary goal of producing their images with milliarcsecond resolution. These sources are brighter than 18 magnitude at V band, and they were previously detected at the European VLBI network. In this paper coordinates of observed sources have been derived with milliarcsecond accuracies from analysis of these VLBI observations following the method of absolute astrometry. The catalogue of positions of 105 target sources is presented. The accuracies of sources coordinates are in the range of 0.3 to 7 mas, with the median 1.1 mas.