Parsec-scale properties of the peculiar gigahertz-peaked spectrum quasar
  0858-279
  We performed multi-frequency studies on the gigahertz-peaked spectrum
high-redshift quasar 0858-279. Initially, the source presented itself in the
early VLBI images as a very peculiar resolved blob. We observed the quasar with
the VLBA at 1.4-24 GHz in a dual-polarization mode. The high spatial resolution
and the spectral index maps enabled us to resolve the core-jet structure and
locate a weak and compact core by its inverted spectrum. The dominant jet
component 20 parsecs away from the core was optically thin above 10 GHz and
opaque below it. We also estimated an uncommonly strong magnetic field in the
bright jet feature, which turned out to be around 1 G. The Faraday rotation
measure maps revealed high RM values over 6000 rad/m^2. Additionally, these
maps allowed us to follow the magnetic field direction in the bright jet
feature being perpendicular to the propagation direction of the jet. All the
results strongly indicated the formation of a shock wave in the dominant
component arising from an interaction with the surrounding matter. Using the
proposed hypothesis and the core shift approach, we discovered that the
magnetic field in the core region is of the order of 0.1 G.
