I. Grenier GSFC ’06
2D binned likelihood2D binned likelihoodsource detectionsource detection
2D binned likelihood2D binned likelihoodsource detectionsource detection
Jean-Marc Casandjian
CEA Saclay
I. Grenier GSFC ’06
2D binned likelihood with DC22D binned likelihood with DC22D binned likelihood with DC22D binned likelihood with DC2
GOAL: find a fast way to get good enough source fluxes and positions
• in particular a good position
• compare with the current unbinned likelihood performance
use of the EGRET program LIKE (fortran, Mattox et al. 1994)
• not fast !!!
binning 0.5° x 0.5° energy bands:
• 100MeV - 200GeV
• 300MeV - 1GeV
• 1GeV - 200GeV
input generated with gtcntsmap, gtmodelmap and exposure_map
• LAT PSF assuming E-2.3 sources
• counts and exposure maps for the whole period
• Galactic interstellar emission maps
I. Grenier GSFC ’06
sky tesselationsky tesselationsky tesselationsky tesselation
45 regions of interest in (l,b) and (,)
for each RoI and energy band: 4 likelihood maps iteratively computed
012345678
101112131415161718
202122232425262728
303132333435363738
404142434445464748
I. Grenier GSFC ’06
iterations 1 & 2iterations 1 & 2iterations 1 & 2iterations 1 & 2
I. Grenier GSFC ’06
interations 3 & 4interations 3 & 4interations 3 & 4interations 3 & 4
I. Grenier GSFC ’06
I. Grenier GSFC ’06
DC2 sourcesDC2 sourcesDC2 sourcesDC2 sources
extended sources detected soft sources detected twice
I. Grenier GSFC ’06
coordinate problemcoordinate problemcoordinate problemcoordinate problem
offset problem between the gtmodelmap binning and LIKE’s interpretation of it
all sources along Gal. plane shifted by 0.25°
I. Grenier GSFC ’06
distance (deg)
Flux difference (%)
catalogue vs. 2D resultscatalogue vs. 2D resultscatalogue vs. 2D resultscatalogue vs. 2D results
df resulting from binning
d < 1 bin typically 0.5° binning ill-adapted at high-
energy
• will be updated soon
I. Grenier GSFC ’06
conclusionsconclusionsconclusionsconclusions
running time estimate of ~ 12 hours with a small 10 cpu cluster for an optimized program
energy-dependent binning to get precise fluxes and positions for a large range of spectral indices
• 0.5° x 0.5° binning enough for a quick-look search for potential source candidates reasonably bright transient search
I. Grenier GSFC ’06
=qhi.HI + qco.WCO + qicIC + qsou.Sources + Cst
qhiHI =qhi01.HI_01 + qh2i.HI_2 + qhi3.HI_3 + qhi4.HI_4 + qhi5.HI_5 + qhi6.HI_6 + qhi78.HI_78
IC still low