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Basic Information on linmos
Purpose: Linear mosaicing of datacubes
Categories: map combination
LINMOS is a MIRIAD task which performs a simple linear mosaicing of
input cubes, to produce a single output cube. If only a single
input cube is given, LINMOS essentially does primary beam correction
on this input. When several, overlapping, inputs are given, then
LINMOS combines the overlapping regions in such a way as to minimize
the rms error in the output.
To determine the primary beam of the telescope, LINMOS first checks
the map header for the presence of the "pbtype" and then "pbfwhm"
parameters. If present, LINMOS assumes the primary beam is the
given type. If these parameters are missing, LINMOS checks if the
telescope is one that it knows. If so, then the known form for the
primary beam is used. See task "pbplot" to check LINMOS's primary
This gives the names of the input cubes. Many cubes can be given.
There is no default. Inputs should generally be on the same grid
system. However, if they are not, linear
interpolation is performed to regrid using the first image as the
template. LINMOS's ability to do this is quite inferior to task REGRID.
The intensity units of all the inputs, and the pixel size
and alignment of the third dimension are assumed to be the same.
The name of the output cube. No default. The center and pixel size
of the first input image is used as the grid system of the output.
The rms noise levels in the input cubes. The default is determined
from the input images. If this is not possible for an image,
then the rms of the previous image is used. If no value could be
determined for the first image, all images are given equal weight.
Extra processing options. Several can be given, separated by
commas. Minimum match is supported. Possible values are:
taper By default, LINMOS fully corrects for primary
beam attenutation. This can cause excessive noise
amplification at the edge of the mosaiced field.
The `taper' option aims at achieving approximately
uniform noise across the image. This prevents full
primary beam correction at the edge of the mosaic.
See equation 2 in Sault, Staveley-Smith and Brouw, A&AS,
120, 376 (1996) or use "options=gains" to see the form
of the tapering.
sensitivity Rather than a mosaiced image, produce an image
giving the rms noise across the field.
gain Rather than a mosaiced image, produce an image
giving the effective gain across the field. If
options=taper is used, this will be a smooth function.
Otherwise it will be 1 or 0 (blanked).