[ Basic Info | User Guide ]
Basic Information on cclean
Purpose: Complex (Polarization) Clean
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
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.
The input Stokes Q and U dirty maps, which should have units of
Jy/beam. No default.
The input of Stokes I, Q or U dirty beam. No default
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).
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)
The minor iteration loop gain. Default is 0.1.
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.
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
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.
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.
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
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
Generated by email@example.com on 30 Nov 2018