Hubble Space Telescope Near Infrared Snapshot Survey of 3CR radio source
  counterparts III: Radio galaxies and quasars in context
  We compare the near-infrared (NIR) H band photometric and morphological
properties of low-redshift (z<0.3) 3CR radio galaxies with samples of BL Lac
object and quasar host galaxies, merger remnants, quiescent elliptical
galaxies, and brightest cluster galaxies drawn from the literature. In general
the 3CR host galaxies are consistent with luminous (~L*) elliptical galaxies.
The vast majority of FR II's (~80%) occupy the most massive ellipticals and
form a homogeneous population that is comparable to the population of
radio-loud quasar (RLQ) host galaxies in the literature. However, a significant
minority (~20%) of the 3CR FR II's appears under-luminous with respect to
quasar host galaxies. All FR II objects in this faint tail are either unusually
red, or appear to be the brightest objects within a group. We discuss the
apparent differences between the radio galaxy and RLQ host galaxy populations.
RLQs appear to require >1E11 M_sun host galaxies (and ~1E9 M_sun black holes),
whereas radio galaxies and RQQs can exist in galaxies down to 3E10 M_sun. This
may be due to biases in the measured quasar host galaxy luminosities or
populations studied, or due to a genuine difference in host galaxy. If due to a
genuine difference, it would support the idea that radio and optical active
galactic nucleii are two separate populations with a significant overlap.
