An optical spectroscopic survey of the 3CR sample of radio galaxies with
  z<0.3. V. Implications for the unified model for FRIIs
  We explore the implications of our optical spectroscopic survey of 3CR radio
sources with z<0.3 for the unified model (UM) for radio-loud AGN, focusing on
objects with a FRII radio morphology. The sample contains 33 high ionization
galaxies (HIGs) and 18 broad line objects (BLOs). According to the UM, HIGs,
the narrow line sources, are the nuclearly obscured counterparts of BLOs. The
fraction of HIGs indicates a covering factor of the circumnuclear matter of 65%
that corresponds, adopting a torus geometry, to an opening angle of 50+/-5
degree. No dependence on redshift and luminosity on the torus opening angle
emerges. We also consider the implications for a 'clumpy' torus. The
distributions of radio luminosity of HIGs and BLOs are not statistically
distinguishable, as expected from the UM. Conversely, BLOs have a radio core
dominance, R, more than ten times larger than HIGs, as expected in case of jet
Doppler boosting. Modeling the R distributions leads to an estimate of the jet
bulk Lorentz factor of Gamma ~3-5. The test of the UM based on the radio source
size is not conclusive due to the limited number of objects. Studying the
emission line ([OIII], [OII]and [OI]) properties of HEGs and BLOs, we find
evidences of a narrow line region (NLR) density stratification and its partial
obscuration from the torus. In conclusion, the radio and NLR properties of HIGs
and BLOs are consistent with the UM predictions. We also explored the radio
properties of 21 3CR FRII low-ionization galaxies (LIGs) at z<0.3. We find that
they cannot be part of the model that unifies HIGs and BLOs, but they are
instead intrinsically different source, still reproduced by a randomly oriented
population.
