DOI

https://doi.org/10.48717/dbze-d755

Project

ET048

Title

ET048A

Abstract

An intensive comparison of the fundamental reference frames - radio (ICRF) and optical (Gaia) - has been undertaken by different groups. A large number of geodetic radio sources (presumably, extragalactic AGNs) with large radio-optical offsets, from 10 to 500 mas and larger, was found. This positional misalignment exceeds the uncertainty of each individual technique (about 1-2 mas for the typical objects). The extended structure of the radio sources is likely to be responsible for the appearance of the large offsets. However, as the data analysts focus on achieving the best possible angular resolution, the large-scale structure is often missed. In some cases, the distant parts of the radio structure are not properly detected due to a lack of short baselines. We are aiming to detect the large-scale structure of a sample of radio sources with extremely large radio-optical offsets by observing of the candidates with the EVN and e-MERLIN at 5 GHz. Successful imaging of such structures will hint that the inconsistency between the two fundamental reference frames is mostly driven by the complex structure at radio frequencies, and efforts are required to solve this problem.