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