Doppler Boosting May Have Played No Significant Role in the Finding Surveys of Radio-Loud Quasars

摘要

There appears to be a fundamental problem facing Active Galactic Nuclei (AGN) jet models that require highly relativistic ejection speeds and small jet viewing angles to explain the large apparent superluminal motions seen in so many of the radio-loud quasars with high redshift. When the data are looked at closely it is found that, assuming the core component is unboosted, only a small percentage of the observed radio frequency flux density from these sources can be Doppler boosted. If the core component is boosted the percentage of boosted to unboosted flux will be higher but will still be far from the 90 percent required for Doppler boosting to have played a significant role. Without a highly directed, Doppler boosted component that dominates the observed flux, radio sources found in low-frequency finding surveys cannot be preferentially selected with small jet viewing angles. The distribution of jet orientations will then follow the sini curve associated with a random distribution, where only a very few sources (~1%) will have the small viewing angles ( 10c, and this makes it difficult to explain how around 33% of the radio-loud AGNs with high redshift can exhibit such highly superluminal motions. When the boosted component is the dominant one it can be argued that in a flux limited sample only those members with small viewing angles would be picked up while those with larger viewing angles (the un-boosted ones) would be missed. However, this is not the case when the boosted component is small and a new model to explain the high apparent superluminal motions may be needed if the redshifts of high-redshift quasars are to remain entirely cosmological.