Pks 1510−089: a Head-on View of a Relativistic Jet

The gamma-ray blazar PKS 1510−089 has a highly superluminal milli-arcsecond jet at a position angle (PA) of −28 and an arcsecond jet with an initial PA of 155. With a ∆PA of 177 between the arcsecond and milliarcsecond jets, PKS 1510−089 is perhaps the most highly misaligned radio jet ever observed and serves as a graphic example of projection effects in a highly beamed relativistic jet. Here we present the results of observations designed to bridge the gap between the milli-arcsecond and arcsecond scales. We find that a previously detected “counter-feature” to the arcsecond jet is directly fed by the milli-arcsecond jet. This feature is located 0.3 from the core, corresponding to a de-projected distance of 30 kiloparsecs. The feature appears to be dominated by shocked emission and has an almost perfectly ordered magnetic field along its outside edge. We conclude that it is most likely a shocked bend, viewed end-on, where the jet crosses our line of sight to form the southern arcsecond jet. While the bend appears to be nearly 180 when viewed in projection, we estimate the intrinsic bending angle to be between 12 and 24. The cause of the bend is uncertain; however, we favor a scenario where the jet is bent after it departs the galaxy, either by ram pressure due to winds in the intracluster medium or simply by the density gradient in the transition to the intergalactic medium. Subject headings: galaxies : active — galaxies: jets — galaxies: kinematics and dynamics — quasars: individual: PKS 1510−089