The catalogue of positions of optically bright extragalactic radio sources OBRS-2

TL;DR

This paper presents a catalogue of 295 optically bright extragalactic radio sources with milliarcsecond position accuracies, aiding future space-based optical and radio coordinate system comparisons and investigations of emission centroid shifts.

Contribution

It provides the first detailed VLBI-based catalogue of bright extragalactic sources with precise positions and flux densities, supporting cross-mission astrometric calibration.

Findings

Median position accuracy of 3.2 mas

Catalogue includes 295 sources with flux density estimates

Positions range from 2 to 200 mas

Abstract

It is anticipated that future space-born missions, such as Gaia, will be able to determine in optical domain positions of more than 100,000 bright quasars with sub-mas accuracies that are comparable to very long baseline interferometry (VLBI) accuracies. Comparisons of coordinate systems from space-born missions and from VLBI will be very important, first for investigation of possible systematic errors, second for investigation of possible shift between centroids of radio and optical emissions in active galaxy nuclea. In order to make such a comparison more robust, a program of densification of the grid of radio sources detectable with both VLBI and Gaia was launched in 2006. In the second observing campaign a set of 290 objects from the list of 398 compact extragalactic radio sources with declinations greater -10 deg was observed with the VLBA+EVN in 2010-2011 with the primary goal of producing their images with milliarcsecond resolution. These sources are brighter than 18 magnitude at V band. 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 and their images were produced. The catalogue of positions of 295 target sources and estimates of their correlated flux densities at 2.2 and 8.4 GHz is presented. The accuracies of source coordinates are in a range of 2 to 200 mas, with the median 3.2 mas.