A Recollimation Shock in a Stationary Jet Feature with Limb-brightening
  in the Gamma-ray Emitting Narrow-line Seyfert 1 Galaxy 1H 0323+342
  We report the discovery of a local convergence of a jet cross section in the
quasi-stationary jet feature in the gamma-ray-emitting narrow-line Seyfert 1
galaxy (NLS1) 1H 0323+342. The convergence site is located at approximately 7
mas (corresponding to the order of 100 pc in deprojection) from the central
engine. We also found limb-brightened jet structures at both the upstream and
downstream of the convergence site. We propose that the quasi-stationary
feature showing the jet convergence and limb-brightening occurs as a
consequence of recollimation shock in the relativistic jets. The
quasi-stationary feature is one of the possible gamma-ray-emitting sites in
this NLS1, in analogy with the HST-1 complex in the M87 jet. Monitoring
observations have revealed that superluminal components passed through the
convergence site and the peak intensity of the quasi-stationary feature, which
showed apparent coincidences with the timing of observed gamma-ray activities.
