The subtraction of images after the deconvolution has been performed. In this method, all the channels are CLEANed independently, then SQASH is used to add together line-free channels and COMB to combine the SQASHed maps from each portion of the line-free spectrum. Finally, COMB is used to subtract the pseudo-continuum from each map. This is most easily done if the channel maps are first combined into a cube.
The 15JAN91 AIPS Cookbook states on page 10-9, "In general, subtraction in the map plane will work fine." However, this statement apparently refers to the subtraction of dirty beams prior to CLEANing, since the Cookbook also warns, "In some cases, e.g., if you have used very broad bandwidth or if you have a very strong continuum source, you might want to do the subtraction in the uv plane."
