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Basic Information on mfspin
Purpose: Compute spectral index from a MFCLEAN model.
MFSPIN is a MIRIAD task that computes spectral index and
possibly rotation measure images, given models produced by
MFCLEAN. It does this by convolving both the flux and "flux
time spectral index" planes of the models by a Gaussian, and
then performing a division.
It can also handle 'pre-convolved' images with flux and flux
times spectral index planes such as those produced by restor
with options=mfs or linmos with options=alpha.
It has two modes of operation. One is to give a single input
model (Stokes I or V even) which consists of two planes. MFSPIN
will then compute the spectral index image from that. The
second mode requires both Stokes Q and U models. MFSPIN will
then compute a linearly polarized intensity spectral index and
optionally a rotation measure image.
The model produced by MFCLEAN. No default. Normally this will
be a single image such as a model for Stokes I or V. However,
you can also give it two models, one for Stokes Q and one for
Stokes U (see the discussion above). If the input already has
units of 'JY/BEAM' (e.g. output from restor with options=mfs)
the convolution step is skipped.
The input dirty beam. This is only required to determine the
beam size. If the fwhm parameter is given, or the input is
already convolved, the beam will not be used.
The division clip level. One or two numbers can be given. If
two values are given, then flux pixel values in this range are
flagged as bad before the division (but after the convolution!).
If a single value is given, then for Stokes I images (or images
for which the Stokes parameter is unknown), all pixel values
less than the specified clip are flagged. If one value is given
and the image is of Stokes Q, U, or V, then pixels are flagged
when their absolute value is less than the clip level.
The default is 0.
The size, in arcsec, of the gaussian beam to convolve with.
This will normally be two numbers, giving the
full-width at half-maximum of the major and minor axes of the
gaussian. If only one number is given, the gaussian will have
equal major and minor axes. If no values are given, they are
computed by fitting a gaussian to the given dirty beam.
The position angle, in degrees, of the Gaussian, measured east
from north. The default is determined from the dirty beam fit
(The value for PA is ignored, if no value is given for FWHM).
Extra processing options. Several can be given, separated by
commas. Minimum match is used. Possible options are:
pbcorr Correct the spectral index for primary beam effects.
By default, this is not performed.
The output image names. No default. Normally this will be a
single output, being the spectral index. If the input consists
of a Q and a U model, the output can be two names. The first is
the linearly polarized intensity spectral index image, and the
second will receive an estimate of the rotation measure (units
Revision: 1.10, 2013/10/22 03:34:26 UTC
Generated by firstname.lastname@example.org on 21 Jun 2016