Basic Information on cclean

Task: c
Purpose: Complex (Polarization) Clean
Categories: deconvolution

        CCLEAN is a MIRIAD task that performs the complex Steer, Hogbom
        or Clark Clean algorithm, which takes a Stokes Q and U
        dirty map and beam, and produces two output maps that consist
        of the Stokes Q and U Clean components.
        These outputs can be input to RESTOR to produce a "clean" image.
        The model could be from a previous CCLEAN run, or from other
        deconvolution tasks.
 
        The main difference with the standard Clean is that the search
        for a peak is done in linearly polarized intensity.
        Full details of the algorithm are found in:
        Pratley & Johnston-Hollitt, "An improved method for
        polarimetric image restoration in interferometry",
        MNRAS, 2016. ArXiv: 1606.01482.
        Please acknowledge this work in publications using the code.
 

Key: map
        The input Stokes Q and U dirty maps, which should have units of
        Jy/beam. No default.

Key: beam
        The input of Stokes I, Q or U dirty beam. No default

Key: model
        Initial models of the Stokes Q and U deconvolved images. This
        could be the output from a previous run of CCLEAN, or the output
        of other deconvolution tasks. It must have flux units of
        Jy/pixel. The default is no model (i.e. a zero map).

Key: out
        The names of the Stokes Q and U output map. The units of the
        output will be Jy/pixel.  The files will contain the contribution
        of the input models.  They should have a different name to the
        input model (if any).  They can be input to RESTOR or CCLEAN
        (as a model,to do more cleaning)

Key: gain
        The minor iteration loop gain. Default is 0.1.

Key: options
        Extra processing options. Several can be given, separated
        by commas. Minimum match is used. Possible values are:
          asym      The beam is asymmetric.  By default CLEAN assumes
                    the beam has a 180 degree rotation symmetry, which
                    is the norm for beams in radio-astronomy.
          pad       Double the beam size by padding it with zeros. This
                    will give you better stability if you are daring
                    enough to CLEAN an area more than half the size
                    (in each dimension) of the dirty beam.

Key: cutoff
        CLEAN finishes either when the absolute maximum residual falls
        below CUTOFF, or when the criteria described below is
        satisfied. The default CUTOFF is 0. It is recommended that the
        cutoff is 3 times the rms noise of Stokes Q or U.
        When two values are given, do a deep clean to the second cutoff
        limiting peak finding to the pixels that are already in the
        model.

Key: niters
        The maximum number of minor iterations.  The default is 250,
        which is too small for all but the simplest of images.  CLEAN
        will stop when either the maximum number of iterations is
        performed, or the cutoff (see above) is reached. Optional second
        value will force CCLEAN to report on the level reached and
        (for mode=clark) start a new major iteration at least every
        niters(2) iterations. This can be useful to avoid overcleaning.

Key: region
        This specifies the region to be Cleaned.  See the help on
        region for more information.  The default is the largest
        region that can be deconvolved safely.

Key: mode
        This can be either "hogbom", "steer" or "any", and
        determines the Clean algorithm used. If the mode is "any", then
        CLEAN determines which is the best algorithm to use. The default
        is "any".

Key: clip
        This sets the relative clip level in Steer mode. Values are
        typically 0.75 to 0.9. The default is image dependent.
 
Revision: 1.3, 2018/11/29 23:30:11 UTC