Image Massaging

Typically there are too few counts in an image, even after combining multiple exposures, to produce a pretty image without smoothing and/or binning. The XMM-ESAS package provides an adaptive filter task, binadapt, which will produce a reasonable background-subtracted and exposure-corrected image (a pretty picture).

binadapt prefix=comb elow=350 ehigh=1100
withpartbkg=true withswcxbkg=true withspbkg=true
withmask=false withbinning=true binfactor=2
withsmoothing=true smoothingcounts=50

The call is mostly as in the previous example, but with a few exceptions. The smoothingcounts=50 defines the smoothing kernel for the adaptive smoothing, while binning=2 sets the number of (linear) pixels for binning the image before the smoothing. maskthresh=0.02 sets the threshold for excluding low exposure regions of the image, the

Figure 30 displays the resultant background-subtracted and exposure-corrected image without (upper panel) and with (lower panel) point-source exclusion. If individual exposures are being smoothed the prefix (e.g., prefix=1S003) as defined above must be entered. The algorithm uses a conical weighting for the smoothing, and a image is created providing the conical FWHM in arc minutes (Figure 31).

Figure 31: Smoothing FWHM for the Abell 1795 image (Figure 30) in the $0.4-1.25$ keV band. The color table is in units of arc minutes.