On the BL Lacertae objects/radio quasars and the FRI/II dichotomy
  In the frame of unification schemes for radio-loud active galactic nuclei
(AGNs), FR I radio galaxies are believed to be BL Lacertae (BL Lac) objects
with the relativistic jet misaligned to our line of sight, and FR II radio
galaxies correspond to misaligned radio quasars. The Ledlow-Owen dividing line
for FR I/FR II dichotomy in the optical absolute magnitude of host galaxy-radio
luminosity (M_R-L_Rad) plane can be translated to the line in the black hole
mass-jet power (M_bh-Q_jet) plane by using two empirical relations: Q_jet-L_Rad
and M_bh}-M_R. We use a sample of radio quasars and BL Lac objects with
measured black hole masses to explore the relation of the jet power with black
hole mass, in which the jet power is estimated from the extended radio
emission. It is found that the BL Lac objects are clearly separated from radio
quasars by the Ledlow & Owen FR I/II dividing line in the M_bh-Q_jet plane.
This strongly supports the unification schemes for FR I/BL Lac object and FR
II/radio quasar. We find that the Eddington ratios L_bol/L_Edd of BL Lac
objects are systematically lower than those of radio quasars in the sample with
a rough division at L_bol/L_Edd 0.01, and the distribution of Eddington ratios
of BL Lac objects/quasars exhibits a bimodal nature, which imply that the
accretion mode of BL Lac objects may be different from that of radio quasars.
