Diffuse Galactic -ray emission model
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Diffuse Galactic -ray emission model. Igor V. Moskalenko (Stanford) with S. Digel (SLAC) T. Porter (UCSC) O. Reimer (Stanford) A. W. Strong (MPE). Diffuse Galactic Gamma-ray Emission. ~80% of total Milky Way luminosity at HE !!! - PowerPoint PPT Presentation
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Diffuse Galactic -ray emission modelIgor V. Moskalenko (Stanford)withS. Digel (SLAC)T. Porter (UCSC) O. Reimer (Stanford) A. W. Strong (MPE)
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Diffuse Galactic Gamma-ray Emission~80% of total Milky Way luminosity at HE !!!Tracer of CR (p, e) interactions in the ISM (0,IC,bremss):Study of CR species in distant locations (spectra & intensities)CR acceleration (SNRs, pulsars etc.) and propagationEmission from local clouds local CR spectraCR variations, Solar modulationMay contain signatures of exotic physics (dark matter etc.)Cosmology, SUSY, hints for accelerator experimentsBackground for point sources (positions, low latitude sources)Besides:Diffuse emission from other normal galaxies (M31, LMC, SMC)Cosmic rays in other galaxies !Foreground in studies of the extragalactic diffuse emissionExtragalactic 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
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Conventional model vs EGRET data4a-fConventional model consistent with local p,e spectra exhibits the GeV excess: a factor ~20 ICBremssEGWe must have at least 2 diffuse emission models with/without the excess
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST 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 & positronsPulsar/SNR source distributionGradient 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 * March 2, 2006DC2/SLACGLAST LAT Project
GeV excess: Optimized/Reaccleration modelUses all sky and antiprotons & gammas to fix the nucleon and electron spectra
Uses antiprotons to fix the intensity of CR nucleons @ HEUses gammas to adjustthe nucleon spectrum at LEthe intensity of the CR electrons (uses also synchrotron index)Uses EGRET data up to 100 GeVprotonselectronsx4x1.8antiprotonsEk, GeVEk, GeVEk, GeVpbarse+ -flux-raysStrong etal 2004
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Secondary e are seen in -rays !Lots of new effects !Improves an agreement at LEbremsICHeliosphere: e+/e~0.2electronspositronssec.
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Distribution of interstellar gasNeutral interstellar medium most of the interstellar gas mass21-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 spectrumThis is the best but far from perfect distance measure availableSelf-absorption of HI (21cm) and optical depth effectsDame et al.(1987)Hartmann &Burton (1997)(25, 0)W. KeelCOH IG.C.25
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
New H2 maps (S.Digel)
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
New HI maps (S.Digel)
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Interstellar Radiation FieldTarget for CR leptons (IC)Energy losses
Systematic errors:Star distribution star countsGrain properties lab measurementsGas/dust proportion extinction curveReasonable parametersCompare with ISRF data only at R Model components:Geometrical: disk, ring, halo, bar, triaxial bulge, arms87 stellar types (main sequence), AGB & exoticsDust: silicate, graphite, PAH (5 few m)Absorbed light gives mid-IR (small grains +PAH) and FIR (~0.1-1 m grains)SMR00PS05Old modelLocal ISRF (PS05)R=0OpticalScatt.opt.IRPAH4 kpc12 kpc16kpc
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Distribution of CR Sources & Gradient in the CO/H2CR distribution from diffuse gammas (Strong & Mattox 1996)SNR distribution (Case &Bhattacharya 1998)sunXCO=N(H2)/WCO:Histo This work, Strong et al.04------Sodroski et al.95,971.9x1020 -Strong & Mattox96~Z-1 Boselli et al.02~Z-2.5 -Israel97,00, [O/H]=0.04,0.07 dex/kpcPulsar distribution Lorimer 2004
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Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Inner Galaxy regionComparison with EGRET & COMPTEL spectral dataOther regions demonstrate equally good agreement
Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
Convolution with EGRET PSF: Important below 1 GeVA large effect at low energies especially in latitude affecting the overall spectral shapeConvolution itself is model dependent -depends on spectrum, not fully accounted for
Model comparison with data
Igor V. Moskalenko * March 2, 2006DC2/SLACGLAST LAT Project
UnconvolvedConvolvedLongitude profile |b|
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