Diffuse Galactic -ray emission model Igor V Moskalenko

Diffuse Galactic -ray emission model Igor V. Moskalenko (Stanford) with S. Digel (SLAC) T. Porter (UCSC) O. Reimer (Stanford) A. W. Strong (MPE)

GLAST LAT Project Diffuse Galactic Gamma-ray Emission ~80% of total Milky Way luminosity at HE !!! Tracer of CR (p, e−) interactions in the ISM (π0, IC, bremss): o o Study of CR species in distant locations (spectra & intensities) CR acceleration (SNRs, pulsars etc. ) and propagation Emission from local clouds → local CR spectra CR variations, Solar modulation May contain signatures of exotic physics (dark matter etc. ) Cosmology, SUSY, hints for accelerator experiments Background for point sources (positions, low latitude sources…) Besides: o “Diffuse” emission from other normal galaxies (M 31, LMC, SMC) Cosmic rays in other galaxies ! o Foreground in studies of the extragalactic diffuse emission o 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 2 March 2, 2006 DC 2/SLAC

Conventional model vs EGRET data 0 Conventional model consistent with local p, e spectra exhibits the “Ge. V excess: ” a factor ~2 2 st ls lea de s at mo ces e av sion ex t h is the s mu e em out e W ffus with di th/ wi Igor V. Moskalenko 3 GLAST LAT Project IC Bremss EG 4 a-f March 2, 2006 DC 2/SLAC

DC 2 diffuse emission model GLAST LAT Project galprop ID = 6002029 RB Based on Strong, Moskalenko, Reimer, 2004, Ap. J 613, 962 Strong, Moskalenko, Reimer, Digel, Diehl, 2004, A&A 422, L 47 Optimized to fit EGRET data (Ge. V excess: CR spectra) Includes secondary electrons & positrons Pulsar/SNR source distribution Gradient in X-factor (H 2/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 Igor V. Moskalenko 4 March 2, 2006 DC 2/SLAC

GLAST LAT Project Ge. V excess: Optimized/Reaccleration model Uses all sky and antiprotons & gammas to fix the nucleon and electron spectra Uses antiprotons to fix the intensity of CR nucleons @ HE Uses gammas to adjust q the nucleon spectrum at LE q the intensity of the CR electrons (uses also synchrotron index) antiprotons ü pbars ü e+ -flux ü γ-rays Uses EGRET data up to 100 Ge. V electrons Ek, Ge. V protons Strong etal 2004 x 1. 8 Ek, Ge. V Igor V. Moskalenko 5 Ek, Ge. V March 2, 2006 DC 2/SLAC

Secondary e± are seen in γ-rays ! GLAST LAT Project Lots of new effects ! electrons Heliosphere: e+/e~0. 2 sec. IC positrons brems Improves an agreement at LE Igor V. Moskalenko 6 March 2, 2006 DC 2/SLAC

GLAST LAT Project Igor V. Moskalenko 7 March 2, 2006 DC 2/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 H 2) (25°, 0°) CO 25° Dame et al. (1987) G. C. HI Hartmann & Burton (1997) W. Keel • 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 (21 cm) and optical depth effects… Igor V. Moskalenko 8 March 2, 2006 DC 2/SLAC

GLAST LAT Project New H 2 maps (S. Digel) Igor V. Moskalenko 9 March 2, 2006 DC 2/SLAC

GLAST LAT Project New HI maps (S. Digel) Igor V. Moskalenko 10 March 2, 2006 DC 2/SLAC

GLAST LAT Project Interstellar Radiation Field • Target for CR leptons (IC) • Energy losses Local ISRF Old model Optical IR 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) Systematic errors: q. Star distribution –star counts q. Grain properties –lab measurements q. Gas/dust proportion –extinction curve q“Reasonable parameters” q. Compare with ISRF data only at R Igor V. Moskalenko 11 (PS 05) March 2, 2006 Scatt. opt. R=0 4 kpc 12 kpc 16 kpc DC 2/SLAC PAH SMR 00 PS 05

GLAST LAT Project Distribution of CR Sources & Gradient in the CO/H 2 Pulsar distribution Lorimer 2004 CR distribution from diffuse gammas (Strong & Mattox 1996) SNR distribution (Case & Bhattacharya 1998) sun XCO=N(H 2)/WCO: Histo –This work, Strong et al. ’ 04 -----Sodroski et al. ’ 95, ’ 97 1. 9 x 1020 -Strong & Mattox’ 96 –Boselli et al. ’ 02 ~Z-1 ~Z-2. 5 -Israel’ 97, ’ 00, [O/H]=0. 04, 0. 07 dex/kpc Igor V. Moskalenko 12 March 2, 2006 DC 2/SLAC

GLAST LAT Project Inner Galaxy region Comparison with EGRET & COMPTEL spectral data Other regions demonstrate equally good agreement Igor V. Moskalenko 13 March 2, 2006 DC 2/SLAC

Model comparison with data GLAST LAT Project Convolution with EGRET PSF: Important below 1 Ge. V 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 Igor V. Moskalenko 14 March 2, 2006 DC 2/SLAC

GLAST LAT Project Effect of Convolution: 70 -100 Me. V Longitude profile |b|<5 Unconvolved Igor V. Moskalenko 15 March 2, 2006 Convolved DC 2/SLAC

GLAST LAT Project Effect of Convolution: 70 -100 Me. V Latitude profile |l|<30 Unconvolved Igor V. Moskalenko 16 March 2, 2006 Convolved DC 2/SLAC

Effect of Convolution: 0. 5 -1 Ge. V GLAST LAT Project Longitude profile |b|<5 Unconvolved Igor V. Moskalenko 17 March 2, 2006 Convolved DC 2/SLAC

Effect of Convolution: 0. 5 -1 Ge. V GLAST LAT Project Latitude profile |l|<30 Unconvolved Igor V. Moskalenko 18 March 2, 2006 Convolved DC 2/SLAC

GLAST LAT Project 1 -2 Ge. V 1000 – 2000 Me. V Convolution effect is negligible Igor V. Moskalenko 19 March 2, 2006 DC 2/SLAC

GLAST LAT Project Effect of De-Convolution: Spectrum |l|<30 |b|<5 “Convolved data” De-convolved 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) Igor V. Moskalenko 20 March 2, 2006 DC 2/SLAC