Parsec-Scale Morphology of PKS 2152-699 and the Radio/Optical Misalignment

We present the first very-long-baseline interferometry (VLBI) image of the parsec-scale structure in the nearby (z=0.0282) Fanaroff-Riley type II radio galaxy PKS 2152-699, revealing the core-jet morphology typical of compact radio sources. Tadhunter et al. [MNRAS, 235, 403 (1988)] have identified this object as one in which the radio axis and optical emission line features on the kiloparsec-scale appear to have an obvious connection but are somewhat misaligned. They interpret this relationship as most likely being due to an interaction between the radio jet and an extra-nuclear cloud of gas, the misalignment possibly caused by the deflection of the radio jet in the interaction. The VLBI observations presented here further strengthen the evidence for the interaction interpretation. The parsec-scale radio jet aligns strongly with optical emission line features, and not with the kiloparsec-scale radio structure. We explore a mechanism which could produce the misalignment and which is consistent with the interaction concept, namely oblique shocks in a relativistic jet. With a minimal model we find that reasonable values of the model parameters can provide the required misalignment over a wide range of initial conditions. © 1996 American Astronomical Society.