PROPERTIES OF THE GAIA-ICRF3 RADIO-OPTICAL REFERENCE FRAME

The radio-optical reference frame tie is based on a few thousand radio-loud quasars listed in the ICRF3 with sufficiently bright optical counterparts to be observed by Gaia. The positions of these sources do not always match within reasonably expected errors; with about 1/5 of the pre-selected sources showing large offsets. We collect a sample of some 2100 quasars; which are not perturbed and appear to be bona fide point-like sources.

With these vetted sources; we perform analysis of the reference frame differences using the vector spherical harmonic decomposition and singular value decomposition. The estimated parameters quantify possible systematic errors; as well as important physical phenomena such as the acceleration of the Solar barycenter. The eigenvalues indicate the weak spots of the current reference frame.