Calibration new MIIRIAD

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pascucci
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Joined: Thu Aug 22, 2013 11:16 am

Calibration new MIIRIAD

Post by pascucci »

Hi, my student and I have reduced the same ATCA dataset at 1cm and 7mm using a MIRIAD package installed at the end of last year AND one installed in June of this year. We realized that there are significant differences in the resulting rms of the images as well as total fluxes of the sources: the newer version of MIRIAD typically delivers lower rms and total fluxes. Note that the two datesets have been reduced using exactly the same data reduction script. Upon inspection of bandpass and gain calibrators we realized that their fluxes are also differences when using the two MIRIAD installations. It seems like mfcal and gpcal have been changed in these two versions going from version 1.13 to 1.14 for mfcal and version 1.14 to 1.15 for gpcal. To give you an idea of the difference at 1cm the total flux of the bandpass calibrator goes from 18.9Jy in the old version to 17.25 Jy in the new version. Similarly the flux of one of the gain calibrators moves from 1Jy to 0.8Jy.

We could not find anywhere what specific upgrades have been made to MIRIAD and how they would affect the fluxes at these wavelengths: Note that previously published data agree with the OLD and not the NEW fluxes.
Does anybody know of a webpage describing pipeline version changes? Has anybody else tested these two different MIRIAD versions and experienced similar issues? How shall we proceed?

Thank you very much.
Best wishes,

Ilaria
Mark.Wieringa
ATCA Expert
Posts: 297
Joined: Mon Feb 08, 2010 1:37 pm

Re: Calibration new MIIRIAD

Post by Mark.Wieringa »

Dear Ilaria,

thanks for your report. I had a look at the changes between the old and new gpcal and mfcal and it doesn't look like they could explain the difference. Miriad has many subroutines which also change from time to time so the change could be further down. I'd like to try and recreate the problem. Could you send me the details of the observations (date/project code), calibrators and the reduction script?
You can send this by email if you prefer.

Cheers,

Mark
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