Changes between Version 5 and Version 6 of PeakCullingInPSPHOT

Timestamp:

Mar 15, 2011, 4:23:03 PM (15 years ago)

Author:

eugene

Comment:

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PeakCullingInPSPHOT

@@ -13 +13 @@
 In the past, the test for the col significance has been made using the raw (unsmoothed) signal and variance images.  However, as defined, any col is significant if it passes below a minimum threshold, defined as a number of sigma above sky.  The result of this definition is that any low-significance peak in a region of low-significance sky flux excursions will always be considered 'significant'.  
 
-In the cases illustrated on the previous page ([wiki:Background_Oversubtraction Background Model), the background excursions are small, but are made significant by smoothing the image when generating the detection image.  Typically, the variations in background in the example are a few to 10 DN, while the sky noise is ~35DN.  The only reason peaks are detected in this region is that image is smoothed with a PSF of width ~10 pixels, pumping up the S/N in the sky, or equally, driving the sky noise from 35DN down to ~1.5DN.  At this level, 10DN excursions are significant.  
+In the cases illustrated on the previous page ([wiki:Background_Oversubtraction Background Model]), the background excursions are small, but are made significant by smoothing the image when generating the detection image.  Typically, the variations in background in the example are a few to 10 DN, while the sky noise is ~35DN.  The only reason peaks are detected in this region is that image is smoothed with a PSF of width ~10 pixels, pumping up the S/N in the sky, or equally, driving the sky noise from 35DN down to ~1.5DN.  At this level, 10DN excursions are significant.  
 
 My idea is that the smoothed image better represents the significance of the background variations.  Thus, if the culling used the smooth signal and variance images, it would probably identify some or many of these low-significance detections as insignificant relative to their neighbors.