Challenges in Astrophysics of CR (knee--) & γ -rays

1. Challenges in Astrophysicsof CR (knee--) & γ-rays Igor V. Moskalenko (Stanford) • Intro to the relevant physics • Some of the challenges… • Modeling of the CR propagation and diffuse emission • Perspectives: Pamela, GLAST and other near future missions

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

3. Volatility Elemental Abundances: CR vs. Solar System CR abundances: ACE O Si Na Fe S CNO Al Cl CrMn LiBeB F ScTiV Solar system abundances Long propagation history…

4. Dark Matter (p,đ,e+,γ) - Nuclear component in CR: What we can learn? Nucleo- synthesis: supernovae, early universe, Big Bang… Stable secondaries: Li, Be, B, Sc, Ti, V Propagation parameters: Diffusion coeff., halo size, Alfvén speed, convection velosity… Radio (t1/2~1 Myr): 10Be, 26Al, 36Cl, 54Mn K-capture:37Ar,49V, 51Cr, 55Fe, 57Co Energy markers: Reacceleration, solar modulation Diffuse γ-rays Galactic, extragalactic: blazars, relic neutralino Short t1/2radio 14C & heavy Z>30 Local medium: Local Bubble Solar modulation Heavy Z>30: Cu, Zn, Ga, Ge, Rb Material & acceleration sites, nucleosynthesis (r-vs. s-processes)

5. 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): • 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: • “Diffuse” emission from other normal galaxies (M31, LMC, SMC) • Cosmic rays in other galaxies ! • Foreground in studies of the extragalactic diffuse emission • 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

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

7. Halo Gas, sources CR Propagation: Milky Way Galaxy 1kpc ~ 3x1018cm Optical image: Cheng et al. 1992, Brinkman et al. 1993 Radio contours: Condon et al. 1998 AJ 115, 1693 100 pc NGC891 40 kpc 0.1-0.01/ccm Halo 1-100/ccm Sun 4-12 kpc Intergalactic space R Band image of NGC891 1.4 GHz continuum (NVSS), 1,2,…64 mJy/ beam “Flat halo” model (Ginzburg & Ptuskin 1976)

8. A Model of CR Propagation in the Galaxy • Gas distribution (energy losses, π0, brems) • Interstellar radiation field (IC, e± energy losses) • Nuclear & particle production cross sections • Gamma-ray production: brems, IC, π0 • Energy losses: ionization, Coulomb, brems, IC, synch • Solve transport equations for all CR species • Fix propagation parameters • “Precise” Astrophysics

9. How It Works: Fixing Propagation Parameters E2 Flux B/C Carbon Radioactive isotopes: Galactic halo size Zh Interstellar Ek, GeV/nucleon Be10/Be9 Ek, MeV/nucleon • Using secondary/primary nuclei ratio & flux: • Diffusion coefficient and its index • Propagation mode and its parameters (e.g., reacceleration VA, convection Vz) Zh increase Ek, MeV/nucleon

10. Peak in the Secondary/Primary Ratio • Leaky-box model: fitting path-length distribution -> free function • Diffusion models: • Diffusive reacceleration • Convection • Damping of interstellar turbulence • Etc. B/C Ek, MeV/nucleon too sharp max? Accurate measurements in a wide energy range may help to distinguish between the models

11. B Distributed Stochastic Reacceleration Simon et al. 1986 Seo & Ptuskin 1994 Scattering on magnetic turbulences Fermi 2-nd order mechanism Dpp~ p2Va2/D D ~ vR1/3 - Kolmogorov spectrum Icr 1/3 ΔE strong reacceleration Dxx = 5.2x1028 (R/3 GV)1/3cm-2 s-1 Va = 36 km s-1 γ ~ R-δ, δ=1.8/2.4 below/above 4 GV weak reacceleration E

12. Convection Escape length Galactic wind Jones 1979 D~R0.6 Xe v R-0.6 wind or turbulent diffusion resonant diffusion E problem:too broad sec/prim peak Dxx = 2.5x1028 (R/4 GV)0.6cm-2 s-1 dV/dz = 10 km s-1 kpc-1 γ ~ R-δ, δ=2.46/2.16 below/above 20 GV

13. Damping of Interstellar Turbulence Kolmogorov cascade: Simplified case: • 1-D diffusion • No energy losses Iroshnikov-Kraichnan cascade: nonlinear cascade Mean free path W(k) dissipation k 1/1020cm 1/1012cm Ptuskin et al. 2003, 2005

14. LiBeB: Major Production Channels Propagated Abundance * Cross-section • Well defined (65%): C12, O16 ->LiBeB N14 -> Be7 (see Moskalenko & Mashnik 28 ICRC, 2003) • Few measurements: C13,N -> LiBeB B -> BeB • Unknown: LiBeB,C13,N -> LiBeB • “Tertiary” reactions also important! -35% Li6 O C 16 12 Li B N Be 13 7 A= 10 9 15 14 11

15. natSi+p26Al ST W 27Al+p26Al W ST Effect of Cross Sections: Radioactive Secondaries Different size from different ratios… • Errors in CR measurements (HE & LE) • Errors in production cross sections • Errors in the lifetime estimates • Different origin of elements (Local Bubble ?) T1/2=? Zhalo,kpc Ek, MeV/nucleon

16. Wherever you look, the GeV -ray excess is there ! EGRET data Excess: x2 4a-f

17. Antiproton flux B/C ratio B/C ratio Antiproton flux Reacceleration Model vs. Plain Diffusion Plain Diffusion (Dxx~β-3R0.6) Diffusive Reacceleration Excess: x2

18. Positron Excess ? HEAT (Beatty et al. 2004) • Are all the excesses connected somehow ? • A signature of a new physics (DM) ? Caveats: • Systematic errors ? • A local source of primary positrons ? • Large E-losses -> local spectrum… e+/e e+/e E > 6 GeV GALPROP HEAT 2000 HEAT 1994-95 HEAT combined GALPROP 10 1 1 10 E, GeV E, GeV Excess: 20% Q: Are all the excesses connected? A: “Yes” and “No” Systematic errors of different detectors Same progenitor (CR p or DM) for pbars, e+’s, γ’s

19. CR Source Distribution Lorimer 2004 Pulsars SNR source CR after propagation diffuse γ-ray distribution The CR source (SNRs, pulsars) distribution is too narrow to match the CR distribution in the Galaxy assuming XCO=N(H2)/WCO=const (CO is a tracer of H2)

20. CR Abundances at LE & HE (ACE vs HEAO-3) • Fitting to measured CR abundances in the wide energy range (~0.1 – 30 GeV) is problematic. • May indicate: • systematic or cross-calibration errors • different origin of LE and HE CR • =(Calcs-Exp)/Exp Fit quality Relat. deviation

21. Hypotheses… Provide good agreement with all data (diffuse gammas, pbars, e+) • CR intensity variations • Dark Matter signals Other possibilities: Harder CR spectrum (protons, electrons) – deviates limits from pbars, gamma-ray profiles Influence of the Local Bubble (local component) – helps with pbars, but doesn’t help with diffuse gammas

22. Diffuse emission models Cosmic Ray Spectral Variations EGRET “GeV Excess” Dark Matter from Hunter et al. ApJ (1997) from Strong et al. ApJ (2004) from de Boer et al. A&A (2005) • 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. 0.5-1 GeV >0.5 GeV

23. SNR number density R, kpc CR Variations in Space & Time More frequent SN in the spiral arms sun Historical variations of CR intensity: ~40kyr (10Be in South Polar ice), ~2.8Myr (60Fe in deep sea FeMn crust) Konstantinov et al. 1990 Electron/positron energy losses Different “collecting” areas A vs. p (σ~30 mb) (different sources ?)

24. Electron Fluctuations/SNR stochastic events GeV electrons 100 TeV electrons GALPROP/Credit S.Swordy Electron energy loss timescale: 1 TeV: ~300 kyr 100 TeV: ~3 kyr Energy losses Bremsstrahlung E(dE/dt)-1,yr Ionization IC, synchrotron Coulomb 107 yr 1 GeV 1 TeV 106 yr Ekin, GeV

25. GeV excess: Optimized/Reaccleration model antiprotons 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 • the nucleon spectrum at LE • the intensity of the CR electrons (uses also synchrotron index) • Uses EGRET data up to 100 GeV • pbars • e+ -flux • γ-rays Ek, GeV protons electrons x4 x1.8 Ek, GeV Ek, GeV

26. Secondary e± are seen in γ-rays ! Lots of new effects ! electrons Heliosphere: e+/e~0.2 sec. IC positrons brems Improves an agreement at LE

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

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

29. Latitude Profiles: Inner Galaxy 0.5-1 GeV 2-4 GeV 50-70 MeV 4-10 GeV 20-50 GeV

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

31. Anisotropic Inverse Compton Scattering • Electrons in the halo see anisotropic radiation • Observer sees mostly head-on collisions Energy density e- R=4 kpc small boost & less collisions e- head-on: large boost & more collisions Z, kpc γ γ γ Important @ high latitudes ! sun

32. Extragalactic Gamma-Ray Background EGRB in different directions Predicted vs. observed E2xF Sreekumar et al. 1998 Elsaesser & Mannheim, astro-ph/0405235 Strong et al. 2004 E, MeV • Blazars • Cosmological neutralinos

33. Distribution of CR Sources & Gradient in the CO/H2 CR distribution from diffuse gammas (Strong & Mattox 1996) SNR distribution (Case & Bhattacharya 1998) Pulsar distribution Lorimer 2004 sun XCO=N(H2)/WCO: Histo –This work, Strong et al.’04 ----- -Sodroski et al.’95,’97 1.9x1020 -Strong & Mattox’96 ~Z-1 –Boselli et al.’02 ~Z-2.5 -Israel’97,’00, [O/H]=0.04,0.07 dex/kpc

34. Again Diffuse Galactic Gamma Rays Very good agreement ! More IC in the GC –better agreement ! 2-4 GeV The pulsar distribution vs. R falls too fast OR larger H2/CO gradient

35. E.Bloom’05

36. Matter, Dark Matter, Dark Energy… Ω≡ρ/ρcrit Ωtot =1.02 +/−0.02 ΩMatter =4.4% +/−0.4% ΩDM =23% +/−4% ΩVacuum =73% +/−4% SUSY DM candidate has also other reasons to exist -particle physics… “Supersymmetry is a mathematically beautiful theory, and would give rise to a very predictive scenario, if it is not broken in an unknown way which unfortunately introduces a large number of unknown parameters…” Lars Bergström (2000)

37. Where is the DM ?! What (flavors): • Neutrinos ~ visible matter • Super-heavy relics: “wimpzillas” • Axions • Topological objects “Q-balls” • Neutralino-like, KK-like Where (places): • Galactic halo, Galactic center • The sun and the Earth How (tools): • Direct searches • low-background experiments (DAMA, EDELWEISS) • neutrino detectors (AMANDA/IceCUBE) • Accelerators (LHC) • Indirect searches • CR, γ’s (PAMELA,GLAST,BESS) from E.Bloom presentation

38. Example “Global Fit:” diffuse γ’s, pbars, positrons GALPROP/W. de Boer et al. hep-ph/0309029 • Look at the combined (pbar,e+,γ) data • Possibility of a successful “global fit” can not be excluded -non-trivial ! Supersymmetry: • MSSM (DarkSUSY) • Lightest neutralino χ0 • mχ ≈ 50-500 GeV • S=½ Majorana particles • χ0χ0−> p, pbar, e+, e−, γ γ pbars e+

39. Longitude and Latitude Distr. E >0.5 GeV Out of the plane (± 300 in long..) In the plane (± 50 in lat.)

40. z Rotation Curve x y DM halo 2003, Ibata et al, Yanny et al. disk bulge Inner Ring Outer Ring Executive Summary –de Boer et al. astro-ph/0408272 Observed Profile: EGRET data + GALPROP Expected Profile (NFW) xy xy Isothermal Profile v2M/r=cons. and M/r3 1/r2 for const. rotation curve xz xz Halo profile

41. PAMELA: Secondary to Primary ratios • LE: sec/prim peak: one instrument -no cross calibration errors • HE: Dxx(R) plots: M.Simon Page Number

42. PAMELA positrons After 3 years • A factor of 2 will become statistically significant • Measuring absolute flux not ratio • Solar minimum conditions

43. PAMELA antiprotons After 3 years

45. A.Morselli

46. GLAST LAT simulations EGRET intensity (>100 MeV) |b| < 20° LAT simulation (>100 MeV) Seth Digel

47. Simulated LAT (>1 GeV, 1 yr) Simulated LAT (>100 MeV, 1 yr) GLAST LAT: The Gamma-Ray Sky This is an animation that steps from 1. EGRET (>100 MeV), to 2. LAT (>100 MeV), to 3. LAT (>1 GeV) EGRET (>100 MeV) Seth Digel

48. B/C Be10/Be9 Zh increase Ek, MeV/nucleon Ek, MeV/nucleon Conclusions I Accurate measurements of nuclear species in CR, secondary positrons, antiprotons, and diffuse γ-rays simultaneously may provide a new vital information for Astrophysics – in broad sense, Particle Physics, and Cosmology. Hunter et al. region: l=300°-60°,|b|<10° Gamma rays: GLAST is scheduled to launch in 2007 – diffuse gamma rays is one of its priority goals Dark Matter CR species:New measurements at LE & HE simultaneously(PAMELA, Super-TIGER, AMS…)

49. Conclusions II Antiprotons: PAMELA (2006), AMS (2008) and a new BESS-polar instrument to fly a long-duration balloon mission (in 2004, 2006…), we thus will have more accurate and restrictive antiproton data HE electrons:Several missions are planned to target specifically HE electrons Positrons: PAMELA (2006), AMS (2008): accurate and restrictive positron data CERN Large Hadronic Collider – will address SUSY In few years we may expect major breakthroughs in Astrophysics and Particle Physics !

50. Thank you !