Is the superluminal motion of compact sources a consequence of the dynamics of propagation of thermal instabilities?

Abstract

VLBI maps of such sources as 3C 273 and 3C 345 show that these sources contain a diffuse jet-like feature in which are embedded knots with apparent superluminal motion. Over the last few years, evidence has increased against the standard beaming relativistic model for explaining superluminal motion. In these models, extremely relativistic flows with velocity ratios β_J²≡V_J²/c² ≈ 0.84 - 0.99 are required. The authors examine a basically nonrelativistic model where the knots are formed by a synchrotron radiation thermal instability. They investigate the possibility that the apparent superluminal motion is a fruit of the dynamics of propagation of the instability.