MONITORING THE BIDIRECTIONAL RELATIVISTIC JETS OF THE RADIO GALAXY 1946+708

We report on a multifrequency, multi-epoch campaign of Very Long Baseline Interferometry (VLBI) observations of the radio galaxy 1946+708 using the Very Long Baseline Array and a Global VLBI array. From these high-resolution observations, we deduce the kinematic age of the radio source to be ~4000 years, comparable with the ages of other Compact Symmetric Objects. Ejections of pairs of jet components appears to take place on time scales of ten years and these components in the jet travel outward at intrinsic velocities between 0.6c and 0.9c. From the constraint that jet components cannot have intrinsic velocities faster than light, we derive H 0 > 57 km s–1 Mpc–1 from the fastest pair of components launched from the core. We provide strong evidence for the ejection of a new pair of components in ~1997. From the trajectories of the jet components, we deduce that the jet is most likely to be helically confined, rather than being purely ballistic in nature.