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Basic Information on pmosmem


Task: pmosmem
Purpose: Maximum Entropy deconvolution for polarization mosaics
Categories: deconvolution

        PMOSMEM is a MIRIAD task that performs a joint maximum entropy
        deconvolution of polarized mosaiced images. Optionally it can
        perform a joint deconvolution with a single dish image as well.
 

Key: map
        Two to five input images.  The first must be a Stokes-I mosaic,
        then one or more polarized mosaics (Stokes Q, U and V images),
        and then optionally a Stokes-I single dish image.  These should
        have units of Jy/beam.  The mosaics should be produced by
        INVERT's mosaic mode.  All the images must be on exactly the
        same pixel grid.  If necessary, use REGRID to make this so.

Key: beam
        One or perhaps two input dirty beams.  The first, corresponding
        to the mosaics, will be produced by INVERTs mosaic mode.  There
        is no default.  The second dirty beam (which must be given if
        there are two dirty map inputs) gives the point-spread function
        of the single dish dirty map.  This second dirty beam need not
        be the same image size as the input dirty maps, and may be
        appreciably smaller.  This single-dish beam is assumed to be
        position-independent, but it need not be symmetric.

Key: default
        The default image.  This is the Stokes-I 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 to produce a restored
        image, or alternatively to PMOSMEM, as a model, to continue the
        deconvolution process.

Key: niters
        The maximum number of iterations. The default is 30.

Key: region
        This specifies the region to be deconvolved.  See the User's
        Manual for instructions on how to specify this.  The default is
        the entire image.

Key: tol
        Tolerance of solution. There is no need to change this from the
        default of 0.01.

Key: q
        One or two values (corresponding to the mosaic and single dish
        observations).  These give estimates of the number of points per
        beam.  PMOSMEM can usually come up with a good, image-dependent
        estimate.

Key: rmsfac
        PMOSMEM must be able to the theoretical rms noise of the input
        dirty map(s), and will, by default, attempt to reduce the
        residuals to have the same rms as this.  If the true rms noise
        is different from the theoretical, you may give the factor to
        multiply by to convert from theoretical to true rms noise.
 
        The theoretical rms will usually be an optimistic estimate of
        the true noise level.  The true noise will be increased by
        calibration errors, confusion, poorly understood distant
        sidelobes, etc.  The rmsfac factor gives some "fudge factor"
        (usually greater than 1) to scale the theoretical noise estimate
        by.  Either one or two values can be given, with the second
        value corresponding to the single dish input.
 
        For a mosaic, the theoretical rms is position dependent, and is
        determined from information save by INVERT (the mostable table).
        For a single dish image, the rms is assumed to be constant
        across the field, and given by the "rms" item in the image.  If
        the single dish input does not contain this item, then this must
        be added before using PMOSMEM.  This is easily done: for image
        xxxx, use
          puthd in=xxxx/rms value=????
        where "????" is the rms noise in Jy/beam.

Key: factor
        The flux calibration factor.  This is only relevant when doing a
        joint deconvolution of a mosaic and a single-dish image.  It
        gives the factor that the single-dish data should be multiplied
        by to convert it to the same flux units as the mosaic.  The
        default is 1.

Key: flux
        An estimate of the integrated flux of the source.  This
        parameter cannot be used if there is an input single dish image.
        Giving PMOSMEM a good value for the integrated flux will help it
        find a good solution.  On the other hand, giving a poor value
        may do harm.  Normally PMOSMEM will NOT constrain the integrated
        flux to be this value, but see the "doflux" option below.  The
        default is image-dependent.

Key: options
        Task enrichment parameters.  Several can be given, separated by
        commas.  Minimum match is used.  Possible values are:
          doflux     Constrain the solution to have the correct
                     integrated flux (normally the integrated flux is
                     not constrained).  The integrated flux is
                     determined from the "flux" parameter or (if no flux
                     parameter is given) from the default image.  This
                     option cannot be used if a single dish input map is
                     also given.
          dofactor   Solve for the flux calibration factor.
          verbose    Give lots of messages during the iterations.  The
                     default is to give a one line message at each
                     iteration.
 
Revision: 1.7, 2016/03/18 03:25:44 UTC

Generated by miriad@atnf.csiro.au on 21 Jun 2016