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 a t 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 Dopple r factors delta < 50. The distribution of delta is consistent with the prev ious results. With the aid of published component motions, we derived a Lor entz 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 th ese sources are on the order of 10(7). An argument is presented based on th ese large boosting factors that the core consists of Doppler-boosted and no n-boosted components. The derived Lorentz factors of the sources exceed the predicted upper bounds of Compton-drag theories.