Estimates and subtracts continuum emission from an image cube
For each (x, y) column in imagename (or a subset selected by region and/or
box), this estimates the continuum by fitting a polynomial to one or more
subsets of the channels. The continuum estimate is saved in contfile, and
subtracted from imagename (or its subset) to make a spectral line estimate,
which is saved in linefile.
Keyword arguments:
imagename -- Input image cube
Default: none; Example: imagename='ngc5921_task.im'
linefile -- Name of output spectral line cube
Default: none; Example: outline='ngc5921_line.im'
contfile -- Name of output continuum cube
Default: none; Example: contfile='ngc5921_cont.im'
fitorder -- Polynomial order for the continuum estimation.
Default: 0; Example fitorder=2
region -- ImageRegion file to select a portion of the cube for output.
Default: '' (= everything)
Example: region='myimage.im.rgn'
region='region1'
Use the viewer on the image cube to define the continuum
regions. This is more general than box but still experimental.
N.B. This is NOT for selecting a subset of the input for
fitting the continuum! Only pixels that are in region
will be considered, however.
box -- A [blcx, blcy, trcx, trcy] region on the directional plane for
selecting a subset for output.
ONLY pixel values are acceptable at this time.
Default: none (whole 2-D plane); Example: box='10,10,50,50'
N.B. This is NOT for selecting a subset of the input for
fitting the continuum! Only pixels that are in region
will be considered, however.
chans -- line-free channel numbers to fit the continuum to.
N.B.: This is currently the _only_ way to specify what is
continuum vs. line emission.
ONLY channel numbers accepted at this time, i.e. there is no
'spw:' as in the spw parameter of other tasks. For
a multi-spw image, the channelization must be the same for all.
Default: '' (all)
Example: chans='3~6;>40'
stokes -- Stokes parameters to image, may or may not be separated
by commas but best if you use commas.
Default: none (all); Example: stokes='IQUV';
Options: 'I','Q','U','V','RR','RL','LR','LL','XX','YX','XY','YY', ... 
1.8.0