[daip] [!7112]: AIPS - AIPS JMFIT: Chi-sq

[Robert Gray]

Robert Gray updated #7112
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AIPS JMFIT: Chi-sq
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           Ticket ID: 7112
                 URL: https://help.nrao.edu/staff/index.php?/Tickets/Ticket/View/7112



Hi!

I'm finding some apparent spectral line features that are (1) noticeably but not dramatically (e.g. 2x) above expected noise peaks and (2) look quire beamlike, and I'm looking for a quantitative method to gauge how beam-like they are.   The ‘chi-sq’ statistic produced by JMFIT looks like it might be the right ticket, but I don’t know how it’s calculated and what the degrees of freedom should be, or how a usually categorical test is being applied to comparing 2D Gaussians.

Can you give me any advice on this, or point me to any publications that cover this application (ideally, ‘Chi-square in VLA Radio Astronomy for Dummies’)?

JMFIT worked great in a test fitting the 100-sigma signal from VGR1 - there was nothing left in the residuals. 

Thanks a lot!

Bob Gray


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