Abstract A relativistic beaming model has been successfully used to explain the observed properties of active galactic nuclei (AGNs). In this model there are two emission components, a boosted one and an unbeamed one, shown up in the radio band as the core and lobe components. The luminosity ratio of the core to the lobe is defined as the core-dominance parameter (R = {LCore}/{LLobe}). The de-beamed radio luminosity (Ldbjet) in the jet is assumed to be proportional to the unbeamed luminosity (Lub) in the co-moving frame, i.e., f = {Ldbjet}/{Lub}, and f is determined in our previous paper. We further discuss the relationship between BL Lacertae objects (BLs) and flat spectrum radio quasars (FSRQs), which are subclasses of blazars with different degrees of polarization, using the calculated values of the ratio f for a sample of superluminal blazars. We found 1) that the BLs show smaller averaged Doppler factors and Lorentz factors, larger viewing angles and higher core-dominance parameters than do the FSRQs, and 2) that in the polarization-core dominance parameter plot (P-log R) the BLs and FSRQs occupy a scattered region, but in a revised plot (log {P}/{c(m)}-log R), they gather around two different lines, suggesting that they have some different intrinsic properties.

Keywords active galactic nuclei -- superluminal motion -- jets -- relativistic beaming model

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