A Constraint on the Standard Beaming Model for Superluminal Sources

Abstract

We have used two subsamples of superluminal quasars to test the relativistic beaming model, and to place useful constraints on the radio source orientation hypothesis and cosmology. Based on the variation of the observed ratio R of the core-to-lobe radio luminosities with proper motion mu for the subsample of lobe-selected quasars, we show that the observed R - mu data can be explained in terms of a bulk relativistic motion with Lorentz factor gamme approx 4. Also, from the observed proper motion versus redshift (mu - z) plot for this subsample, we show that gamma approx 4 implies a high density universe with deceleration parameter q_0 = 0.5. Furthermore, from the observed (mu - z) plot for the two subsamples taken separately, we show that both gamma and mu for the core-selected subsample exceed those of the lobe-selected subsample by a factor of 2 for the q_0 = 0.5 world model. This result is demonstrated to be consistent with an orientation-based unified scheme in which lobe-selected quasars lie, on the average, at an angle which is a factor of ~2-3 larger than that of their core-selected counterparts.