Motion Statistics in the CJ Survey -- The Status in October 2002

Abstract

In the Caltech-Jodrell Survey of bright flat-spectrum radio sources, 3-5 epochs have now been observed for nearly all 293 sources; a uniquely large sample. The derivation of component motions has not yet been completed; it is complicated by, for example, variability and jet curvature. Nevertheless, some basic results are clear. The average apparent velocity in CJF quasars is near 3c, while for radio galaxies and BL Lacs it is around 1c. The distribution of velocities is broad, indicating a broad distribution of jet Lorentz factors, with many low values, and/or a decoupling of the Lorentz factors between the cores and the moving jet components, due to bending, speed changes, or due to pattern motions (shocks). A hint has emerged at this workshop that the average apparent velocities might be lower at lower radio frequencies; this will need careful verification.