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Basic Information on maxen
Task: maxen
Purpose: Maximum Entropy deconvolution
Categories: deconvolution
MAXEN is a MIRIAD task which performs a maximum entropy deconvolution
algorithm on a cube.
Key: map
The input dirty map, which should have units of Jy/beam. No default.
Key: beam
The input dirty beam. No default
Key: model
An initial estimate of the deconvolved image. For point sources,
giving a good initial model may help convergence. In principle,
this only helps convergence, but should not affect the final
solution. The model could be the output from a previous run of
MAXEN or any other deconvolution task. It must have flux units of
Jy/pixel. The default is a flat estimate, with the correct flux.
Key: default
The default image. This is the image that the final solution will
tend towards. The final result will be influenced by this default
if the constrains that the data put on the solution are weak.
The default is a flat estimate, with the correct flux.
Key: out
The name of the output map. The units of the output will be Jy/pixel.
It can be input to RESTOR, MAXEN (as a model, to continue the
deconvolution process), or to SELFCAL (for self-calibrating
visibility data).
Key: niters
The maximum number of iterations. The default is 20.
Key: region
This specifies the region to be deconvolved. See the Users Manual
for instructions on how to specify this. The default is the largest
centered region that it is safe to deconvolve.
Key: measure
The entropy measure to be used, either "gull" (-p*log(p/e)) or
"cornwell" (-log(cosh(p)) -- also called the maximum emptyness
criteria).
Key: tol
Tolerance of solution. There is no need to change this from the
default of 0.01.
Key: q
An estimate of the number of points per beam. MAXEN can usually
come up with a pretty good, image dependent estimate.
Key: rms
The rms noise, in Jy/beam, in the dirty map. No default. The
convergence and behavior of MAXEN depends strongly on the value
of this parameter.
Key: flux
The flux of the source. If FLUX is given as a positive
number, then the resultant image is constrained to have this
flux. If FLUX is negative, then abs(FLUX) is used as an estimate
of the source flux only and the actual flux is allowed to vary.
If FLUX=0, then MAXEN makes a guess at the source flux. Default is
FLUX=0, though you should give MAXEN more information if at all
possible. On the other hand, a bad value here can cause MAXEN to
blow up.
Key: options
Task enrichment parameters. Several can be given, separated by
commas. Minimum match is used. Possible values are:
quiet Do not give any messages during iterations. The default
is to give a one line message at each iteration.
verbose Give lots of messages during the iterations. The default
is to give a one line message at each iteration.
asym The beam is asymmetric. By default MAXEN assumes the
beam has 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 better stability if you are daring enough
to deconvolve more than the inner quarter of the dirty
image.