Tests of pointing offsets and background subtraction for M82

The sharpinteg-sharp_combine pipeline is used to create I-maps of M82. To do this accurately we must determine and correct for the telescope pointing offets. Larry has written an IDL code to find these offsets, but they have a very large scatter. The maps below show some results.

An I-map of M82 using only files labeled as "2" and "3" in Larry's fit to the galaxy shape. Pointing corrections are generated by this fit code. A smoothing kernal of 2'' FWHM was used to make this image and co-adds 58 files.

Left: Same as figure above but the large scatter in the fit-code pointing corrections have been removed by hand.
Right: Same as figure at left above but Larry has background subtracted all 57 images before input to sharp_combine.

Same as figures above but now showing polarization vectors; q and u maps were smoothed with a 10'' FWHM kernal. All vectors shown have ΔP<2%. Red vectors are P/ΔP > 2, green vectors P/ΔP < 2. Vectors are drawn every ~ 4.5 arcsec. (Left: no background subtraction. Right: with background subtraction)