[daip] [Fwd: AIPS questions]

[Amy Mioduszewski]

-------- Original Message --------
Subject: AIPS questions
Date: Wed, 9 Nov 2005 17:00:14 +0100 (MET)
From: Magdalena Kunert-Bajraszewska <magda at astro.uni.torun.pl>
To: Amy Mioduszewski <amiodusz at nrao.edu>



Dear Amy,

I have some questions about the data processing in AIPS:

1. In a case of one of my sources (VLBA 15 GHz) after the first run of
FRING (for phase calibrator) there is nothing on the map. So I used
6cm image of this source as a model in FRING, and I got something on the
map, the coordinates of this structure is consistent with this what I
can see on the other frequencies. I used aparm(7)=3 and dparm(2)=500
dparm(3)=100 , and I got 13% of bad solutions. Maybe the question is naive
but I don't have much experience, but Can I believe this structure is real
and not generated by FRING?

2. Should I always run FRING on my target source with a phase-referenced
map as a model ? Suppose that I did this but this map is worse than the
phase-referenced one (higher rms and the peak flux density of my source is
lower). Does it mean the source was too weak for this and I should treat
the phase-referenced map as a final?

3. I have noticed that for some of my sources there is a diffrence in
coordinates between 18 and 6 cm in order of 0.004 arcseconds. There is no
such difference for instance between 6 and 4 cm. What is the reason for
that? Could it be the slightly different structure of the phase calibrator
on different frequencies? What can I do to adjust the coordinates?

Best wishes,

Magdalena