Gamma-rays in flat-spectrum AGN: Revisiting the fast jet hypothesis with
  the CJF sample
  The recent release of the First Fermi-LAT Source Catalog solidified the
predominant association of extragalactic gamma-ray emitters to active galaxies,
in particular blazars. A tight connection between AGN jet kinematics and
gamma-ray properties has been argued for, attributing the energetic emission
from active galaxies to their highly relativistic outflows. We investigate the
Caltech-Jodrell Bank flat-spectrum (CJF) sample to study the connection between
AGN jet kinematics and their gamma-ray properties. The high number of sources
included in the sample, in addition to the excellent kinematic data available,
allows us to investigate the origin of gamma-ray emission in AGN. We identify
the CJF sources detected in gamma-rays (by Fermi-LAT and EGRET). We use
gamma-ray luminosities and the available VLBI kinematic data to look for
correlations between gamma-ray and kinematic properties, as well as for
differences between AGN classes (quasars, BL Lacs, radio galaxies). We also
check the kinematics of the TeV sources in the CJF. 21.8% of the CJF has been
detected in the gamma-rays. We find the detectability of BL Lacs significantly
higher compared to quasars. gamma-detected sources show a wider apparent jet
velocity distribution compared to the non-detected ones, but the maxima of both
distributions are at similar values. No strong link between gamma-ray
detectability and fast apparent jet speeds is found. A tentative correlation is
found between gamma-ray luminosity and maximum apparent jet speeds, stronger
for BL Lac and gamma-variable sources. We find non-radial jet motions to be
important to gamma-ray emission. We suggest two-zone, spine-sheath, models as a
possible explanation to our results. We find 2 out of 4 CJF TeV sources show
superluminal jet speeds, in contrast to previous studies.
