[daip] Pband issues

[Lawrence Rudnick]

Gentlemen:

I solicit your wisdom on 2.5 Pband problems.
D configuration, 22 field mosaic (with each pointing
mapped with 61 facets) infinite number of
details available if that is important.

Problem 1.  If I compare Pband fluxes with NVSS fluxes,
there appears to be a significant *offset* at low
fluxes;  i.e., the slope of P vs. NVSS does not
extrapolate to zero.  A plot of the running medians
of sources found in both surveys can be seen at
http://www.astro.umn.edu/~larry/LSS/#bias2

have you seen anything like this before?  I have in
very diffuse sources like Cas A, where we get a bowl
around the outside, but not where field is all
small sources...  (maps available on that same web page)

Problem 2.  If I take the difference image between maps made @
different pointing centers, there are residuals that are
much bigger than the noise (after correcting for primary
beam).  So I picked three strong sources, and measured
their observed fluxes in (almost) all fields, and tried
to see how well things fit the expected primary beam
attenuation.  Results are at:
http://www.astro.umn.edu/~larry/LSS/#primary1

After applying a pb correction and comparing all the fluxes,
the result is that each field looks a little "off", with
most scale factors varying between 2 and 10% of the average.
More description in the figure caption.
Inspiration welcome.

Problem 2.5  Total field was reconstructed using FLATN.
As noted to Eric earlier, LTESS does not appear to be
working properly.

Any wisdom you have would be most appreciated.

larry