On significance of VLBI/Gaia position offsets
  We have cross matched the Gaia Data Release 1 secondary dataset that contains
positions of 1.14 billion objects against the most complete to date catalogue
of VLBI positions of 11.4 thousand sources, almost exclusively active galactic
nuclei. We found 6,064 matches, i.e. 53% radio objects. The median uncertainty
of VLBI positions is a factor of 4 smaller than the median uncertainties of
their optical counterparts. Our analysis shows that the distribution of
normalized arc lengths significantly deviates from Rayleigh shape with an
excess of objects with small normalized arc lengths and with a number of
outliers. We found that 6% matches have radio optical offsets significant at
99% confidence level. Therefore, we conclude there exists a population of
objects with genuine offsets between centroids of radio and optical emission.
