Bug #2268
Background cube overpredicts number of simulated events
| Status: | Closed | Start date: | 10/31/2017 | |
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| Priority: | Urgent | Due date: | ||
| Assigned To: |  Knödlseder Jürgen | % Done: | 100% | |
| Category: | - | |||
| Target version: | 1.5.0 | |||
| Duration: |
Description
The number of predicted background events when using a background cube is too large with respect to the number of simulated events. This is illustrated by the following plots who compare the simulated events for a single 50h long observation towards the Galactic centre to the number of event predicted by ctmodel determined a background cube (top row). For comparison, the background row shows the predicted background events when using directly the IRF, i.e. without going through the stacked background cube. In that case, the predicted number of background events looks fine.
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spectra.png (40 KB)
longitude.png (64.8 KB)
latitude.png (65.9 KB)
spectra_direct.png (37.8 KB)
longitude_direct.png (61.2 KB)
latitude_direct.png (62.7 KB)
spectra_corrected.png (37.8 KB)
longitude_corrected.png (61.2 KB)
latitude_corrected.png (62.7 KB)
spectra_iem.png (38.6 KB)
longitude_iem.png (62.3 KB)
latitude_iem.png (55.5 KB)
Recurrence
No recurrence.
History
#1
Updated by Knödlseder Jürgen about 7 years ago
- File spectra_corrected.png added
- File longitude_corrected.png added
- File latitude_corrected.png added
- Status changed from New to In Progress
- % Done changed from 0 to 90
The origin of the problem was quickly found. In GCTACubeBackground::operator() the background rate was determine using a lin-log interpolation which in GCTABackground3D::operator() a log-log interpolation is used. Since the latter is also used for the event simulation it was required to switch also the GCTACubeBackground::operator() to a log-log interpolation.
After doing this the results are consistent with those obtained using directly the IRFs. The corresponding plots are shown below.
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#2
Updated by Knödlseder Jürgen about 7 years ago
- File spectra_iem.png added
- File longitude_iem.png added
- File latitude_iem.png added
I cross-checked that the computation of a diffuse emission component is okay. The model used here is the 1DC galactic diffuse emission model.
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#3
Updated by Knödlseder Jürgen about 7 years ago
- Status changed from In Progress to Closed
- % Done changed from 90 to 100
Merged code into devel.