2007ApJ...658..232C

Relations between the observed quantities for a beamed radio jet, which are the apparent transverse speed and the apparent luminosity (β_app, L), and the intrinsic quantities, which are the Lorentz factor and the intrinsic luminosity (γ, L₀), are investigated. The inversion from measured to intrinsic values is not unique, but approximate limits to γ and L₀can be found using probability arguments. Roughly half the sources in a flux density-limited, beamed sample have a value of γ close to the measured value of β_app. The methods are applied to observations of 119 AGN jets made with the VLBA at 15 GHz during 1994-2002. The results strongly support the common relativistic beam model for an extragalactic radio jet. The (β_app, L) data are closely bounded by a theoretical envelope, an ``aspect'' curve for γ=32 and L₀=10²⁵ W/Hz. This gives limits to the maximum values of γ and L₀in the sample: γ_max~32, and L_0,max∼10²⁶ W/Hz. No sources with both high values of β_app and low values of L are observed. This is not the result of selection effects due to the observing limits, which are a flux density of S>0.5 Jy and an angular velocity of µ<4 mas/yr. Many of the fastest quasars have a pattern Lorentz factor, γ_p, that is close to that of the beam, γ_b, but some of the slow quasars must have γ_p≪γ_b. Three of the 10 galaxies in the sample have a superluminal feature, with speeds up to β_app~6. The others are at most mildly relativistic. The galaxies are not off-axis versions of the powerful quasars, but Cygnus A might be an exception.