A1731 430 Mhz mapping near coma cluster

Links:

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Intro:

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Tsys for polA,polB changing in 2003,2004

10jan05: Plotting Tsys vs az/za, ra/dec at various steps in the processing (using mapping cals)

• black: ramap  polA
• red   : ramap  polB
• green: decmap  polA
• blue   : decmap  polB

 
• Tsys after bad channels removed and cal used to convert to kelvins

The data was read in, bad channels were flagged, the total power was computed over the good channels, and then it was converted to kelvins using the cals. The plots are:
• 2003 map CA
• 2003 map CB
• 2004 map CA04
• 2004 map CB04
• Plot 2004 maps vs az,za  by day.

The system temperature plots for 2003,2004 showed that the Tsys was changing (or maybe the cal value). The following plots are for Tsys (before any fitting) using color to separate out the different days when the data was taken. You can see that some days gave very different Tsys than others. It would probably be a good idea to fit tsys to the individual days rather than the entire map at once.
• 2004 map CA04 (.ps)   (.pdf)
• 2004 map CB04 (.ps)   (.pdf)
• Fit for Tsys versus za for both fields (ca,cb) together (pola,polb is fit separately).

The next step is to fit for tsys versus za combining the data for fields ca,cb. PolA and polB are fit separately. The fitting iterates throwing away outliers. The plots are:
• 2003 map CA
• 2003 map CB
• 2004 map CA04
• 2004 map CB04
• Gain correct the data and convert to Jy.

After removing Tsys, the data is gain corrected using the gain curve for 430 and then converted to janskies. This will push up the points at higher  za. If tsys has not been removed correctly, then this will worsen the offsets with za.
• 2003 map CA
• 2003 map CB
• 2004 map CA04
• 2004 map CB04
• Grid the data, optionally remove ra ramp in ramap, and then basketweave.

For each source the ra,dec maps were gridded and then the basketweave procedure was used to correct for offsets in the strips.  The process was repeated taking a linear ramp out of the ramap after gridding and before basketweaving.  Each set of plots contains:
• Fig 1. Top ramap before basketweaving, 2nd plot ramap after basketweaving. 3rd plot decmap before basketweaving, 4th  plot dec map after basketweaving.
• Fig 2 This is the same as figure 1 except that a linear ramp was removed from the ramap before basketweaving.
• Fig 3 The basetwoven maps (ra,dec) were then averaged. The top plot is the average with no raramp remove, the bottom plot is the average with the raramp removed from the pre-basketweave ramap.

 
• 2004 map CA04 (after gridding)
• 2004 map CB04 (after gridding)


Looking at the tsys for 2003, 2004 you can see that the system temperature was changing (at least for 1 polarization). This will cause problems when the Tsys is removed because all of the data for a map is fit at one. The outliers will continue to stick out. The jumps in the gridded decmap for ca_04 around ra sample 40 were taken on 11jun04 while the other data was taken 21-25 may04..

 

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