[daip] clean 3bit Ka data

[zadeh]

Hi Eric,
Hope all is well. I may be overlooking something easy but how do I 
include spectral index information in calib for a
point source that varies across the 64 IFs. I am trying to do a phase 
followed by an amplitude selfcal using a point source
model.
I appreciate it.
Farhad


On 1/23/14 11:44 AM, Eric Greisen wrote:
> zadeh wrote:
>> Hi Eric,
>> We have broad band  data sets at Ka band but the flux of the bright 
>> source varies as a function of frequeny as nu^0.3 across the 8GHz of
>> bandwidth. How do I clean this data correctly  or even  self-cal this 
>> data in aips? Any suggestions would be appreciated.
>>
>> Another question. What is the task name to do Faraday depth map and 
>> Faradat RM map? We have  images
>> at multiple frequencies across the band.
>
> Two excellent - nearly research level - questions.
>
> 1. If most of the flux has a single spectral index, then IMAGR will 
> allow you to correct it in the UV data work file using IMAGRPRM(2).
>
>   If there is real structure in spectral index that might matter, you 
> need to do a multiple step procedure.  First IMAGR the data in 
> spectral chunks of modest size.  Take the output images and make a 
> cube with MCUBE or FQUBE. then bring the planes of the cube to the 
> same resolution (usually just the fattest of your beams) with CONVL.  
> Then run SPECR on that cube.   Take the SPECR output as IN3NAME et al 
> (and perhaps IN4NAME if curvature is significant) in an IMAGR that 
> includes all channels/IFs.
> Use FQTOL to make this process run faster and also include the primary 
> beam (IMAGRPRM(1)) when you do this since it won't cost you anything.
>
> 2. RM analysis is definitely a research topic.  The current best 
> answer is to run FARS on your P and Q cubes (corrected for spectral 
> index) (task SPCOR).  Then run RMFIT.
>
> I am about to go back to work on RMFIT to add another parameter to be 
> fit having to do with the thickness of the Faraday screen. that will 
> take a while but you will have much to learn.  The Faraday rotation 
> measure synthesis, done with FFTs, has a very fat point-spread 
> function (beam) and so is no so useful.  But RMFIT is aided with the 
> FARS output and so you must wait for it (FARS is slowwwww).
>
> You may wish to talk to Larry Rudnick (larry at umn.edu) as he is expert 
> on the subject.
>
> Eric Greisen