Total Flux Density Variations in Extragalactic Radio Sources. III. Doppler Boosting Factors, Lorentz Factors, and Viewing Angles for Active Galactic Nuclei

Abstract

We have calculated Doppler boosting factors, for a sample of active galactic nuclei (AGNs) using D var , total Ñux density variation monitoring data at 22 and 37 GHz. We argue that this method is more accurate than the other commonly used methods based on the synchrotron self-Compton X-ray Ñux or equipartition of energy. We compare our Doppler factors with other results and conclude that even if the average for a class of sources is very similar to all others, the variability Doppler factors for D var individual objects are more accurate and reliable. An important application of precise Doppler factors is presented, namely, calculating the Lorentz factors, !, and the viewing angles, h, of relativistic outÑows in AGNs. We Ðnd that high-polarization quasars have the greatest Doppler boosting, while low-polarization quasars and BL Lac objects are less boosted. The two groups of quasars show di †erent characteristics because of di †erent combinations of the Lorentz factor and viewing angle, rather than either a di †erent ! or h alone.