Discovery of large Doppler factors in radio-loud active galactic nuclei

We have studied the Doppler factors of active galactic nuclei. The inverse-Compton effect and equipartition models were applied to VLBI observations at 22 GHz. Total flux density measurements at 43 and 92 GHz were made for a reliable estimation of the Doppler factors. We found that two sources (0235+164, 1921-293) have Doppler factors larger than 80, while most have Doppler factors delta < 50. The distribution of delta is consistent with the previous results. With the aid of published component motions, we derived a Lorentz factor Gamma > 60 for 0235+164, Gamma > 41 for 1921-293, and a viewing angle phi < 1 degrees for both sources. The derived boosting factors of these sources are on the order of 10(7). An argument is presented based on these large boosting factors that the core consists of Doppler-boosted and non-boosted components. The derived Lorentz factors of the sources exceed the predicted upper bounds of Compton-drag theories.