Ag. Polatidis et Pn. Wilkinson, SUPERLUMINAL MOTION IN THE PARSEC-SCALE JET IN 3C-380, Monthly Notices of the Royal Astronomical Society, 294(2), 1998, pp. 327-337
We present extensive multi-epoch VLBI observations of the quasar 3C 38
0 which reveal a bent parsec-scale radio jet with complex substructure
which exhibits superluminal motion out to similar to 100 pc from the
active core. The general characteristics of the jet and its motion are
similar to those in several other well-studied superluminal sources,
most notably a rapid increase in the opening angle at a projected dist
ance of a few tens of parsecs from the core and apparent acceleration
along the jet. This acceleration could be a simple kinematic effect as
sociated with bulk flow at a constant speed, but at a varying angle to
the line of sight. The jet is well resolved in the transverse directi
on for the majority of its length and resembles numerical simulations
of a jet disrupted by the rapid growth of sinusoidal 'Kelvin-Helmholtz
' modes. Our maps also reveal extremely rapid localized variations in
brightness which have not yet been seen in other nuclear jets. We sugg
est that phase effects, arising from the intersection of oblique shock
s, may be the cause of these dramatic changes. 3C 380 is often classif
ied as a compact steep spectrum (CSS) source; however, in contrast to
the majority of CSS sources, it is likely that 3C 380 is simply a powe
rful FRII source seen approximately end-on.