Self-calibration and Continuum Image

The technique of self-calibration can be used to make additional correction for the residual errors in antenna gains using the closure-relation technique. Miriad task selfcal performs self-calibration of visibility data. Either phase only or amplitude and phase calibration can be performed. Usually, it needs a few self-calibration cycles to converge the process. The following example shows the setup of self-calibration with phase only and then amplitude and phase:

selfcal% inp
  Task:   selfcal
  vis      = sgra-star.selfcal   % uv data
  model    = sgra-star.icmp      % model produced from clean
  interval = 10                  % interval of solutions
  options  = phase,mfs           % phase only and mfs
  refant   = 3

After the phase errors be minimized with a few step of self-calibration in phase-only, one may try self-calibration in both amplitude and phase.

selfcal% inp
  Task:   selfcal
  vis      = sgra-star.selfcal   % uv data
  model    = sgra-star.icmp      % model produced from clean
  interval = 20                  % interval of solutions
  options  = amp,mfs             % amp & phase  and mfs
  refant   = 3

Fig.4. shows an image with self-calibration. This image shows Sgr A* and the nearby dust components detected by the SMA at 345 GHz.

Figure: Self-calibrated map: Sgr A* and the dust emission from the circum-nuclear disk at the Galactic center.