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Igor V. Moskalenko (Stanford)Igor V. Moskalenko (Stanford)
withwith
S. Digel (SLAC)S. Digel (SLAC)
T. Porter (UCSC)T. Porter (UCSC)
O. Reimer (Stanford)O. Reimer (Stanford)
A. W. Strong (MPE)A. W. Strong (MPE)
Diffuse Galactic Diffuse Galactic -ray emission -ray emission
modelmodel
Igor V. Moskalenko 2 March 2, 2006 DC2/SLAC
GLAST LAT ProjectDiffuse Galactic Gamma-ray Diffuse Galactic Gamma-ray EmissionEmission
~80% of total Milky Way luminosity at HE !!!
Tracer of CR (p, e−) interactions in the ISM (π0,IC,bremss):o Study of CR species in distant locations (spectra & intensities)
CR acceleration (SNRs, pulsars etc.) and propagationo Emission from local clouds → local CR spectra
CR variations, Solar modulationo May contain signatures of exotic physics (dark matter etc.)
Cosmology, SUSY, hints for accelerator experimentso Background for point sources (positions, low latitude sources…)
Besides:o “Diffuse” emission from other normal galaxies (M31, LMC,
SMC) Cosmic rays in other galaxies !
o Foreground in studies of the extragalactic diffuse emissiono Extragalactic diffuse emission (blazars ?) may contain
signatures of exotic physics (dark matter, BH evaporation etc.)Calculation requires knowledge of CR (p,e) spectra in the entire Galaxy
Igor V. Moskalenko 3 March 2, 2006 DC2/SLAC
GLAST LAT Project
Conventional model vs EGRET data
4a-f
Conventional model consistent with local p,e spectra exhibits the “GeV excess:” a factor ~2
0 ICBremssEG
We must
have at least
2 diffuse emiss
ion
models with
/with
out
the excess
Igor V. Moskalenko 4 March 2, 2006 DC2/SLAC
GLAST LAT Project
galprop ID = 6002029RB
Based onStrong,Moskalenko,Reimer, 2004, ApJ 613,962
Strong,Moskalenko,Reimer,Digel,Diehl, 2004, A&A 422, L47
Optimized to fit EGRET data (GeV excess: CR spectra) Includes secondary electrons & positrons Pulsar/SNR source distribution Gradient in X-factor (H2/CO)
Improvements: new HI, CO data (Digel) new interstellar radiation field (Porter) fine adjustments to reflect these new inputs
Examples of model unconvolved and convolved with EGRET PSF
DC2 diffuse emission model
Igor V. Moskalenko 5 March 2, 2006 DC2/SLAC
GLAST LAT ProjectGeV excess: Optimized/Reaccleration model
Uses Uses all skyall sky and antiprotons & gammas and antiprotons & gammas to fix the nucleon and electron spectrato fix the nucleon and electron spectra
Uses Uses antiprotonsantiprotons to fix to fix the the intensityintensity of CR nucleons @ HE of CR nucleons @ HE
Uses Uses gammasgammas to adjust to adjust the nucleon spectrum at LEthe nucleon spectrum at LE the the intensity intensity of the CR electrons of the CR electrons
(uses also synchrotron index)(uses also synchrotron index)
Uses EGRET data Uses EGRET data up to 100 GeVup to 100 GeV
protonsprotonselectronselectrons
x4x4
x1.8
antiprotonsantiprotons
EEkk, GeV, GeV
EEkk, GeV, GeV
EEkk, GeV, GeV
pbarse+ -fluxγ-rays
Strong etal 2004
Igor V. Moskalenko 6 March 2, 2006 DC2/SLAC
GLAST LAT Project
Secondary e± are seen in γ-rays !
Lots of new effects !
Improves an agreement at LE
brems
IC
Heliosphere: e+/e~0.2
electronselectrons
positronspositrons
sec.
Igor V. Moskalenko 7 March 2, 2006 DC2/SLAC
GLAST LAT Project
Igor V. Moskalenko 8 March 2, 2006 DC2/SLAC
GLAST LAT Project
Distribution of interstellar gas• Neutral interstellar medium – most of the interstellar gas mass
– 21-cm H I & 2.6-mm CO (standing for H2)
• Differential rotation of the Milky Way – plus random motions, streaming, and internal velocity dispersions – is largely responsible for the spectrum
• This is the best – but far from perfect – distance measure available
• Self-absorption of HI (21cm) and optical depth effects…
Dame et al.(1987)
Hartmann &Burton (1997)
(25°, 0°)
W. Keel
CO
H IG.C.
25°
Igor V. Moskalenko 9 March 2, 2006 DC2/SLAC
GLAST LAT Project
New H2 maps (S.Digel)
Igor V. Moskalenko 10 March 2, 2006 DC2/SLAC
GLAST LAT Project
New HI maps (S.Digel)
Igor V. Moskalenko 11 March 2, 2006 DC2/SLAC
GLAST LAT Project
Interstellar Radiation Field
Systematic errors:Star distribution –star countsGrain properties –lab measurementsGas/dust proportion –extinction curve“Reasonable parameters”Compare with ISRF data only at R
• Target for CR leptons (IC)• Energy losses
Model components: Geometrical: disk, ring, halo, bar, triaxial
bulge, arms 87 stellar types (main sequence), AGB &
exotics Dust: silicate, graphite, PAH (5Å – few m) Absorbed light gives mid-IR (small grains
+PAH) and FIR (~0.1-1 m grains)
SMR00PS05
Old model Local ISRF (PS05)
R=0
Optical
Scatt.opt.
IR
PAH
4 kpc
12 kpc
16kpc
Igor V. Moskalenko 12 March 2, 2006 DC2/SLAC
GLAST LAT ProjectDistribution of CR Sources & Gradient in the CO/H2
CR distribution from diffuse gammas (Strong & Mattox 1996)
SNR distribution (Case &Bhattacharya 1998)
sun
XXCOCO=N(H=N(H22)/W)/WCOCO::
Histo –This work, Strong et al.’04----- -Sodroski et al.’95,’971.9x1020 -Strong & Mattox’96~Z-1 –Boselli et al.’02~Z-2.5 -Israel’97,’00, [O/H]=0.04,0.07 dex/kpc
Pulsar distribution Lorimer 2004
Igor V. Moskalenko 13 March 2, 2006 DC2/SLAC
GLAST LAT Project
Inner Galaxy region
Comparison with EGRET & COMPTEL spectral data
Other regions demonstrate equally good agreement
Igor V. Moskalenko 14 March 2, 2006 DC2/SLAC
GLAST LAT Project
Convolution with EGRET PSF: Important below 1 GeV A large effect at low energies especially in
latitude affecting the overall spectral
shape Convolution itself is model dependent -
depends on spectrum, not fully accounted
for
Model comparison with data
Igor V. Moskalenko 15 March 2, 2006 DC2/SLAC
GLAST LAT Project
Unconvolved Convolved
Longitude profile |b|<5
Effect of Convolution: 70-100 MeV
Igor V. Moskalenko 16 March 2, 2006 DC2/SLAC
GLAST LAT Project
Unconvolved Convolved
Latitude profile |l|<30
Effect of Convolution: 70-100 MeV
Igor V. Moskalenko 17 March 2, 2006 DC2/SLAC
GLAST LAT Project
Unconvolved Convolved
Longitude profile |b|<5
Effect of Convolution: 0.5-1 GeV
Igor V. Moskalenko 18 March 2, 2006 DC2/SLAC
GLAST LAT Project
Unconvolved Convolved
Latitude profile |l|<30
Effect of Convolution: 0.5-1 GeV
Igor V. Moskalenko 19 March 2, 2006 DC2/SLAC
GLAST LAT Project
1000 – 2000 MeV1-2 GeV
Convolution effect is negligible
Igor V. Moskalenko 20 March 2, 2006 DC2/SLAC
GLAST LAT Project
NB here the spatial convolution correction is applied to the DATA based on the model. Hence the DATA changes, not the model (procedure appropriate for spectra)
“Convolved data” De-convolved
Effect of De-Convolution: Spectrum |l|<30 |b|<5
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