A procedure for making high dynamic-range radio images: Deep imaging of
  the kiloparsec-scale radio structures of a distant blazar, NRAO 530, with
  JVLA data
  Using JVLA data of Sgr A* and NRAO 530 (as a calibrator) at 5.5, 9 and 33
GHz, we developed a procedure for the reduction of wideband data. We have
demonstrated that, correcting for residual interferometer errors such as
residual delays, astronomers can now achieve high-fidelity radio images with a
dynamic range exceeding 1,000,000:1. We outline the detailed procedure, noting
that it can have broad application to the analysis of broadband continuum
observations. We apply this procedure to observations of a distant blazar, NRAO
530, revealing its structures in unprecedented detail. Our 5.5-GHz image shows
that the structure of NRAO 530 is prominently characterized by a moderately
curved western jet terminating at a hot spot. Close to the radio core, an
abrupt bending of the jet is revealed in the high-resolution (<100 mas) images
at 33 GHz, showing an evolution of the position angle of the jet from the north
at the VLBI scale (50 mas, or ~400 pc projected), increasing toward the west at
the larger VLA scales (1 arcsec, or ~10 kpc). The continuation of the jet axis
drift forms the curved western jet extending out to 20 arcsec. In contrast, a
faint and broad counter-jet is present on the eastern side with a curvature
antisymmetric to the western jet. The eastern jet terminates at a bright
hotspot, forming an edge-brightened diffuse lobe. The observed contrast in
brightness between the western and eastern jets suggests that the jets on the
VLA scale are mildly relativistic. The radiation from the western jet is
boosted while the radiation from the receding eastern jet is plausibly
suppressed owing to the relativistic Doppler effect.
