XMM-Newton Science Analysis System

ssclib (ssclib-4.35) [xmmsas_20211130_0941-20.0.0]

### Parallel detection over bands (with no assumptions made about source spectrum)

Here the situation is a little more complicated. If nothing can be assumed about the spectra of the sources, the best detection strategy appears to be as follows:

• Detect in each band separately.
• Calculate likelihood values according to equation 1.
• Add the band likelihoods together for each position.

This sum over likelihoods itself follows a Poisson-like distribution. It can thus be shown that the overall likelihood for any given value of this sum being not due to chance, ie, the overall likelihood that there is a source at this position, is given by

where approximates a linear function of of slope 1. Monte Carlo studies indicate that , , and so forth; however eboxdetect at the present time assumes that ; hence that (arguably not quite correct) assumption has been built into the present subroutine as well.

    subroutine minDetPoissonCountsVector(bkgCounts, likelihoodCutoff&
, detectableSrcCounts, detectableSrcCountsUncert, srcCountRatios, status)
real(single), intent(in)            :: srcCountRatios(:),&
bkgCounts(size(srcCountRatios)),&
likelihoodCutoff
real(single), intent(out)           :: detectableSrcCounts(&
size(srcCountRatios))
real(single), intent(out)           :: detectableSrcCountsUncert(&
size(srcCountRatios))
integer,      intent(out), optional :: status
end subroutine minDetPoissonCountsVector
end interface minDetPoissonCounts


XMM-Newton SOC -- 2021-11-30