[daip] AIPS help

[Lorant Sjouwerman]

On Thu, 14 Apr 2005 slipnick at brandeis.edu wrote:

#  I am trying to remove a core from three images, and I am having trouble
#doing it.  I have the data as images in Aips, and I want to remove the core,
#I know I can use uvsub and subtract the model of the core from the image, but
#I am =not sure how to make a model of just the core in AIPS, I am wondering
#if you could help. thanks.

Scott,

I can give you some suggestions to try while the real experts are 
currently unavailable. Best thing is to subtract the core from the 
uv data (done with UVSUB) and reimage to get your new maps, but I 
figure at this moment you've passed the imaging step and want to 
subtract a model image from the images (and not a clean component
model from the uvdata).

You can create and subtract models from images in AIPS using IMFIT, 
JMFIT, SAD, IMMOD, COMB and probably one or two more tasks. The key 
is to request the residual image, though I don't think J/IMFIT will 
let you use a large image (use SAD or a multiple of COMB with IMFIT,
SUBIM, OHGEO etc - you can be creative here). Typ 'apropos image' or 
'apropos model' to find more on tasks about imaging or modeling.

Hope this helps for the moment.

Here are some hints if you can go back to reimaging the uvdata
You could make a model (cc model) of the core, for example by

fitting the core in the image (eg with JMFIT), and subtract that
 (the cc model) from the uv data
edit the cc file to only include components in the core area and
 subtract the cc model from the uvdata
reimage with only the longest baselines and/or box around the core
 to do the same as above (as the core is compact I presume) and
 subtract the cc model or the image from the uvdata

Depending on the simplicity of the core I'd start with the first
suggestion and see how it goes before trying a next suggestion.

Regards,

Loránt Sjouwerman - Scientific Services - lsjouwerman at nrao.edu
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