Presentation #106.09 in the session “AGN (Poster)”.
I will present a new effort to mine the VLA archives to measure the proper motions of compact components in kilo-parsec scale jets from active galactic nuclei, where I have analyzed archival VLA observations of radio galaxy 3C 78 for proper motions where we detect for the first time speeds of 0.5-0.7c in multiple knots. We have used a theoretical framework to relate the bulk speed to the speed of the observed pattern, which allowed us to constrain the bulk speed directly. Although sub-luminal, we find that the bulk speed is ~5 times higher than the maximum VLBI speed, in keeping with observations of M87 and 3C 264 which have showed that the fastest bulk speeds in these FR I jets are reached on the > 100 parsec scale. We also find that the jet retains a conical shape from parsec to kilo-parsec scales, in addition to being highly matter-dominated at the hundred parsec scales. Our results suggest that the jet is more likely to be accelerated by a continual conversion of jet internal energy to directed kinetic energy, rather than by conversion of magnetic energy. Our work is the initial step towards creating a Catalogue of proper motions in Active galactic Nuclei with Very Large Array Studies (CAgNVAS) to map their complete velocity profiles from parsec to kilo-parsec scales.