The radio/gamma-ray connection in Active Galactic Nuclei in the era of
  the Fermi Large Area Telescope
  We present a detailed statistical analysis of the correlation between radio
and gamma-ray emission of the Active Galactic Nuclei (AGN) detected by Fermi
during its first year of operation, with the largest datasets ever used for
this purpose. We use both archival interferometric 8.4 GHz data (from the VLA
and ATCA, for the full sample of 599 sources) and concurrent single-dish 15 GHz
measurements from the Owens Valley Radio Observatory (OVRO, for a sub sample of
199 objects). Our unprecedentedly large sample permits us to assess with high
accuracy the statistical significance of the correlation, using a
surrogate-data method designed to simultaneously account for common-distance
bias and the effect of a limited dynamical range in the observed quantities. We
find that the statistical significance of a positive correlation between the cm
radio and the broad band (E>100 MeV) gamma-ray energy flux is very high for the
whole AGN sample, with a probability <1e-7 for the correlation appearing by
chance. Using the OVRO data, we find that concurrent data improve the
significance of the correlation from 1.6e-6 to 9.0e-8. Our large sample size
allows us to study the dependence of correlation strength and significance on
specific source types and gamma-ray energy band. We find that the correlation
is very significant (chance probability <1e-7) for both FSRQs and BL Lacs
separately; a dependence of the correlation strength on the considered
gamma-ray energy band is also present, but additional data will be necessary to
constrain its significance.
