STEP 2: Results 


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Download a plot of STEP2 results
This is the main result plot which shows, for each author analysis (ID key), the parameters m and c for both components of shear. The different colours are for the different PSF models. In those cases, where relevant, the large red triangle is the result from STEP1.
I'm afraid that this plot is a little busy, but the symbols and lines are as follows;
Solid lines = estimates of m and c from gamma
(equation 9c)
dotted lines = estimates of m = (mA + mB)/2 and c=(cA  cB)
where individual errors are added in quadrature and mA etc are
calculated from equation 9a,b
The comparison of the solid and dotted error bars show the difference between statistical shot noise and statistical shear measurement noise.
The circle symbol (o) is positioned at (mA,c)
The triangle symbol is positioned at (mB,c)
The comparison of these two symbols show how stable the shear calibration errors m are to image rotation. Often they are very close, as expected, but in some cases they are very different. Note the same set of matched galaxies are included in both the original and rotated analyses so this is not a selection effect.
Back to the main STEP2 results page
Download more information:
The following data files containing these results can be downloaded;
mc_table.dat contains the results from the full STEP2 analysis which combines the original and rotated images. The format is as follows
ID  PSF  pair selc  1  m1 +/ err  c1 +/ err 
ID  PSF  pair selc  2  m2 +/ err  c2 +/ err 
where the fourth column denotes the shear component.
The files mc_i_table.dat contain slightly more information. The format is as follows
ID  PSF  orig all  m_orig +/ err  c_orig +/ err 
orig selc  mA +/ err  cA +/ err  
rot selc  mB +/ err  cB +/ err  
pair selc  m +/ err  c +/ err 
Columns 45 are simply the plotted points and should be self explanatory (selc means the results come from the matched catalogues). The first row are the results that you would have received back from the original STEP2 analysis which contain all your objects. mc_1_table.dat contains the results for the gamma_1 component. mc_2_table.dat contains the results for the gamma_2 component. Comparing row 1 and row 2 tells you about the effect that matching the original and rotated catalogues have introduced. In general the changes are very small.
The tar file shear_in_out.tar unpacks into individual directories for each author, and plots the measured shear against the input shear for each shear component and PSF. Overplotted are the bestfit lines. Each directory contains 4 files;
Last modified 21st March.
STEP pages maintained by Catherine Heymans: heymans[at]physics.ubc.ca