Summary of chop-nod analysis telecon of June 17, 2009

Giles, Lero, Mike, John, Hiroko


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chi2 inflation flag:

For sky positions where the reduced chi squared (rcs) is < 1, the Q and U 
errors should not be altered at all, as discussed in 2008.  Mike confirmed 
that this issue is handled properly on the version of chi2 currently 
compiled on zamin.

For sky positions where there is insufficient basis for calculating the 
rcs, Mike explained that the inflate option causes the errors to be 
inflated by a very big factor (of order 10000).

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Lero's analysis of M82:

- 8 bins (note: 4 bins and 2 bins where done earlier; see October 2008 
analysis logbook posting)

- chi2 a bit higher than in past

- used update flag to inflate errors

- result is : just one 3-sigma vector

- when threshhold set to 2 or 2.5 sigma, lots of very big vectors, and 
more small ones too

- sharpcombine flags used are nominal (see June 10th e-mail to 
sharp-software); same 55 files as in October.

- presumably, the reason we did not see these huge vectors in the October 
maps is that they were lurking just below the 3-sigma threshhold; 
apparently even after inflation some of them are still above the 2.5 sigma 
threshhold.

Next steps:

- use "scale" to better identify location and size of huge vectors (or use 
new version of polsharp5 that accurately gives locations and sizes)

- plot upper limits

- examine whether cuts on I or on (I/sigma-I) can eliminate huge vectors.  
Note that I and sigma-I for sky positions of huge vectors can be read off 
of sharpcombine-output fits file (see extension for sigma-I).

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Other issues:

Hiroko updated chi2 on puuoo/kilauea

sharpcombine versions: zamin has 5.14, puuoo/kilauea has 5.131 ... John 
will investigate

During the telecon, John put a new version of polsharp5 on zamin which 
correctly outputs the sky positions of the vectors

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