1. Modified from talk of Igor V. Moskalenko (Stanford U.) GALPROP & Modeling the Diffuse  -ray Emission

2. CR Interactions in the Interstellar Medium e + - PHeCNO X,γ gas ISRF e + - π + - P_LiBeB ISM diffusion energy losses energy losses reacceleration reacceleration convection convection etc. etc. π 0 synchrotron IC bremss Chandra GLAST ACE helio-modulation p 42 sigma (2003+2004 data) HESS Preliminary SNR RX J1713-3946 PSF BHeCNO Flux 20 GeV/n CR species:  Only 1 location  modulation e + - π + - PAMELA BESS AMS

3. Diffuse Galactic Gamma-ray Emission ~80% of total Milky Way luminosity at HE !!! Tracer of CR (p, e − ) interactions in the ISM (π 0,IC,bremss): oStudy of CR species in distant locations (spectra & intensities)  CR acceleration (SNRs, pulsars etc.) and propagation oEmission from local clouds → local CR spectra  CR variations, Solar modulation oMay contain signatures of exotic physics (dark matter etc.)  Cosmology, SUSY, hints for accelerator experiments oBackground for point sources (positions, low latitude sources…) Besides: o“Diffuse” emission from other normal galaxies (M31, LMC, SMC)  Cosmic rays in other galaxies ! oForeground in studies of the extragalactic diffuse emission oExtragalactic 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

4. Transport Equations ~90 (no. of CR species) ψ(r,p,t) – ψ(r,p,t) – density per total momentum sources (SNR, nuclear reactions…) convection convection (Galactic wind) diffusion diffusive reacceleration diffusive reacceleration (diffusion in the momentum space) E-loss fragmentation radioactive decay + boundary conditions

5. CR Propagation: Milky Way Galaxy Halo Gas, sources 100 pc 40 kpc 4-12 kpc 0.1-0.01/ccm 1-100/ccm Intergalactic space 1 kpc ~ 3x10 18 cm R Band image of NGC891 1.4 GHz continuum (NVSS), 1,2,…64 mJy/ beam Optical image: Cheng et al. 1992, Brinkman et al. 1993 Radio contours: Condon et al. 1998 AJ 115, 1693 NGC891 Sun “Flat halo” model (Ginzburg & Ptuskin 1976)

6. What it takes to model CR propagation in the Galaxy  Gas distribution (energy losses, π 0, brems)  Interstellar radiation field (IC, e ± energy losses)  Nuclear & particle production cross sections  Gamma-ray production: brems, IC, π 0  Energy losses: ionization, Coulomb, brems, IC, synch  Assume propagation model (Dxx, Dp, Va)  Source distribution & injection spectra  Solve transport equations for all CR species  Fix propagation parameters

7. More Effects: Local Environment Sun Regular Galactic magnetic field may establish preferential directions of CR propagation Sun GC ~200pc Local Bubble:  A hole in the interstellar gas is formed in a series of SN explosions; some shocks may still exist there…  May be important for radioactive CR species, but D xx =?

8. CR Source Distribution SNR source The CR source (SNRs, pulsars) distribution is too narrow to match the CR distribution in the Galaxy assuming X CO =N(H 2 )/W CO =const (CO is a tracer of H 2 ) Lorimer 2004 Pulsars CR after propagation diffuse γ-ray distribution

9. Distribution of CR Sources & Gradient in the CO/H 2 CR distribution from diffuse gammas (Strong & Mattox 1996) SNR distribution (Case & Bhattacharya 1998) sun X CO =N(H 2 )/W CO : Histo –This work, Strong et al.’04 ------Sodroski et al.’95,’97 1.9x10 20 -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

10. Electron Fluctuations/SNR stochastic events GeV electrons 100 TeV electrons GALPROP/Credit S.Swordy Energy losses 10 7 yr 10 6 yr Bremsstrahlung 1 TeV Ionization Coulomb IC, synchrotron 1 GeV Ekin, GeV E(dE/dt) -1,yr Electron energy loss timescale: 1 TeV: ~300 kyr 100 TeV: ~3 kyr

11. Wherever you look, the GeV  -ray excess is there ! 4a-f EGRET data

12. Diffuse  -ray emission models 0.5-1 GeV >0.5 GeV Dark Matter Cosmic Ray Spectral Variations EGRET “GeV Excess” There are two possible BUT fundamentally different explanations of the excess, in terms of exotic and traditional physics:  Dark Matter  CR spectral variations Both have their pros & cons. from Strong et al. ApJ (2004) from de Boer et al. A&A (2005) from Hunter et al. ApJ (1997)

13. GeV excess: Optimized/Reaccleration model Uses all sky and antiprotons & gammas to fix the nucleon and electron spectra  Uses antiproton flux to fix the intensity of CR nucleons @ HE  Uses gammas to adjust  the nucleon spectrum at LE  the intensity of the CR electrons (uses also synchrotron index)  Uses EGRET data up to 100 GeV protons electrons x4 x1.8 antiprotons E k, GeV

14. Diffuse Gammas at Different Sky Regions Intermediate latitudes: l=0°-360°,10°<|b|<20° Outer Galaxy: l=90°-270°,|b|<10° Intermediate latitudes: l=0°-360°,20°<|b|<60° Inner Galaxy: l=330°-30°,|b|<5° Hunter et al. region: l=300°-60°,|b|<10° l=40°-100°,|b|<5° corrected Milagro

15. Longitude Profiles |b|<5° 50-70 MeV 2-4 GeV 0.5-1 GeV 4-10 GeV

16. Latitude Profiles: Inner Galaxy 50-70 MeV 2-4 GeV0.5-1 GeV 4-10 GeV20-50 GeV

17. Latitude Profiles: Outer Galaxy 50-70 MeV 2-4 GeV 0.5-1 GeV 4-10 GeV

18. Example “Global Fit:” diffuse γ’s, pbars, positrons  Look at the combined (pbar,e +,γ) data  Possibility of a successful “global fit” can not be excluded -non-trivial ! pbars e+e+ γ GALPROP/W. de Boer et al. hep-ph/0309029 Supersymmetry:  MSSM (DarkSUSY)  Lightest neutralino χ 0  m χ ≈ 50-500 GeV  S=½ Majorana particles  χ 0 χ 0 −> p, pbar, e +, e −, γ

19. Pohl et al.2003 sun Positions of the local clouds The Excess: Clues from the Local Medium Digel et al.2001 Observations of the local medium in different directions, e.g. local clouds, will provide a clue to the origin of the excess (assuming it exists). Inconclusive based on EGRET data YesNo Poor knowledge of π 0 -production cross section: better understanding of π 0 -production Dark Matter signal: look for spectral signatures in cosmic rays (PAMELA, BESS, AMS) and in collider experiments (LHC) Possibility: cosmic-ray spectral variations. Further test: look at more distant clouds Will GLAST see the excess? EGRET data