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This yields ratios of numbers of events within a nominal 14 degree radius cone about IC 443 of Galactic:Isotropic:IC443 = 10:1:10 for the energy range 20-5000 MeV.
Binned Analysis
Effects near ends of selected energy range with energy dispersion handling turned on
In order to account for events that are mixed from outside the selected energy range, the likelihood code extrapolates the model counts spectrum for each source beyond the emin, emax values specified in gtbin when making the counts cube. Because the effective area is changing strongly as a function of energy below about 100 MeV, this sort of extrapolation can lead to problems modeling the measured spectrum at low energies. The recommended way to mitigate this is to create a counts cube (and corresponding binned exposure map) that extends beyond the desired energy range to be analyzed. The likelihood code will then use the actual exposure to compute the model counts as a function of true energy and the resulting spectra can then be used to compute accurately the model counts in measured energy space. In this analysis, the counts cube and binned exposure map extend from 20 to 5000 MeV, giving sufficient coverage at low and high energies to ensure accurate modeling for the desired analysis covering 60 to 2000 MeV.
The likelihood xml-model definition
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