A panchromatic review of thermal and nonthermal active galactic nuclei
  The first short part of this review is a general, but very detailed, critique
of the literature advocating a class of Seyfert galaxies intrinsically lacking
broad emission lines. My conclusion is that there is little or no evidence for
such objects.
  Panchromatic properties of all types of radio loud AGN are then reviewed in
detail. Radio galaxies usually show subparsec-scale radio core sources, jets,
and a pair of giant radio lobes. The optical spectra sometimes show only
relatively weak lines of low-ionization ionic species, and no clear nuclear
continuum in the optical or UV region of the spectrum. Some show strong
high-ionization narrow lines. Finally, a few radio galaxies add broad bases
onto the permitted lines. These spectral categories are the same as those for
radio-quiet AGN and quasars.
  By the 1980s, data from optical polarization and statistics of the radio
properties required that many narrow line radio galaxies do in fact produce
strong optical/UV continuum. This continuum and the broad line emission are
hidden from the line of sight by dusty, roughly toroidal gas distributions, but
they are seen in polarized flux. The radio galaxies with hidden quasars are
referred to as "thermal."
  Do all radio galaxies harbor hidden quasars? We now know the answer using the
radio, infrared, optical and X-ray properties. Near the top of the radio
luminosity function, for FRII, GPS, and CSS galaxies, the answer is yes. At
somewhat lower luminosities, many do not. At the lowest radio luminosities,
most do not. Instead these "nonthermal" weakly-accreting galaxies manifest
their energetic output only as kinetic energy in the form of synchrotron jets.
This applies to all types of radio galaxies, big FR II doubles, as well as the
small young GPS and CSS sources. Only a few FR I sources are of the thermal
type.
