Extended radio emission in core-dominated quasars: implications for relativistic beaming hypothesis

This paper investigates a simple consequence of relativistic beaming and radio source orientation scenario for high-luminosity extragalactic radio sources, based on the distributions of core-luminosity (P C ) and extended lobe luminosity (P E ) in a sample of core-dominated quasars (CDQs). In this scenario, CDQs are believed to have their radio axes oriented at closer angles to the line of sight relative to their parent population of FR II radio galaxies. At this orientation, the core emission is greatly enhanced due to relativistic Doppler boosting and linear size (D) foreshortened due to geometrical projection. A simple outcome of this is that the extended luminosity is expected to be orientation invariant. Our results show a fairly strong anti-correlation (r∼−0.5) between the core-to-lobe luminosity ratio (R), believed to be orientation dependent, and P E . Based on the assumption that FR II radio galaxies form the parent population of the CDQs, the observed R–P E anti-correlation in the CDQs is consistent with a bulk Lorentz factor in the range γ≈3–5 and cone angle for optimum beaming 11∘≤ϕ c ≤17∘, for continuous jet model. Furthermore, there is a weak D–P E anti-correlation (r∼−0.3). The results are consistent with relativistic beaming at largest scales, although intrinsic/asymmetries in the local environments cannot be completely ruled out.