The parsec-scale structure and evolution of the nearby Fanaroff-Riley typeII radio galaxy Pictor A

We present very long baseline interferometry (VLBI) images of the core emis sion from a nearby bright FR II radio galaxy, Pictor A, revealing its parse c-scale jet structure and evolution for the first time. These data constitu te a significant addition to our knowledge of powerful radio galaxies on th e smallest scales, effectively doubling the number studied at this resoluti on. The jet, 14 h(-1) pc in projected extent, is directed west of the core for the first 5 h(-1) pc and then appears to bend approximately 40 degrees to the north. Apparent motions for three of the five parsec-scale jet compo nents have been estimated, 0.5 +/- 0.4, 1.1 +/- 0.5, and 0.4 +/- 0.7 h(-1)c , indicating that subluminal motion is likely. No parsec-scale counterjet h as been detected, allowing only lower limits on the jet-to-counterjet surfa ce brightness ratio to be estimated. Two models, one describing the apparen t 40 degrees bend in the parsec-scale jet as an intrinsic deflection of the jet and one describing it as the effect of jet precession, may each be pla usible and should be testable with future VLBI observations. By adopting th e jet deflection model to describe the apparent 40 degrees bend, we estimat e that the Pictor A jet is initially inclined to our line of sight by less than 51 degrees. Comparing this result with VLBI observations of Cygnus A s uggests that, while the components in both jets are consistent with at leas t mildly relativistic speeds, the Pictor A jet lies significantly closer to our line of sight than the Cygnus A jet. This conclusion is consistent wit h both the parsec-scale radio structures and the kiloparsec-scale orientati ons of the host galaxies as well as the "unified model" interpretation of t he optical spectra from these two objects.