Indirect Evidence for Dark Matter from Galactic Gamma Rays

1. Indirect Evidence for Dark Matter from Galactic Gamma Rays DM what is it? We don’t know it, because we don’t see it! WdB, C. Sander, V. Zhukov, A. Gladyshev, D. Kazakov, EGRET excess of diffuse Galactic Gamma Rays as Tracer of DM, astro-ph/0508617, A&A, 444 (2005) 51

2. Do we have Dark Matter in our Galaxy? Rotationcurve Solarsystem rotation curve Milky Way

3. How much Dark Matter in Universe? If it is not dark, it does not matter SNIa sensitive to acceleration, i.e.  - (SM+ DM) Dark Matter: Grav. attractive Dark Energy: Grav. repulsive (if dρ/dt=0!) = ρ / ρcrit = B+ DM + =1 23±4% of energy in Universe = DM (WIMPS) CMB sensitive to overall density, i.e.  + SM + DM)

4. T>>M: f+f->M+M; M+M->f+f T<M: M+M->f+f T=M/22: M decoupled, stable density (wenn Annihilationrate  Expansions- rate,i.e. =<v>n(xfr)  H(xfr) !) Expansion rate of universe determines WIMP annihilation cross section Thermal equilibrium abundance Actual abundance Comoving number density WMAP -> h2=0.1130.009 -> <v>=2.10-26 cm3/s DM increases in Galaxies: 1 WIMP/coffee cup 105 <ρ>. DMA (ρ2) restarts again.. Annihilation into lighter particles, like Quarks and Leptons -> 0’s -> Gammas! T=M/22 Only assumption in this analysis: WIMP = THERMAL RELIC! x=m/T Jungmann,Kamionkowski, Griest, PR 1995

5.    f f f ~ f A Z    f f f   W Z 0    Z W Example of DM annihilation (SUSY) ≈37 gammas Quark-Fragmentation known! Hence spectra of positrons, gammas and antiprotons known! Relative amount of ,p,e+ known as well. Dominant  +   A  b bbar quark pair Sum of diagrams should yield <σv>=2.10-26 cm3/s to get correct relic density

6. Idea of analysis Idea: Thermal relics disappeared by annihilation. (From WMAP Annihilation cross section <σv>=2.10-27/Ωh2) Annihilation into Quarks with this x-section should yield large amount of Gamma Rays (37γ’s/Annihilation from LEP data) Gamma spectrum from DMA significantly harder than dominant background from inelastic pp collisions (Cosmic Rays on H-gas) Background shape KNOWN from fixed target experiments, DMA Gamma Ray shape KNOWN from LEP data EGRET Data indeed shows such an expected excess with expected spectral SHAPE IN ALL SKY directions and INTENSITY of excess allows to measure DM distribution in GALAXY. Then one knows MASS distribution of DM and visible matter and can calculate ROTATION CURVE (RC). IF GAMMA RAYS indeed originate from DMA, then this can be proven by calculating shape of RC from Gamma Rays! WdB, C. Sander, V. Zhukov, A. Gladyshev, D. Kazakov, EGRET excess of diffuse Galactic Gamma Rays as Tracer of DM, astro-ph/0508617, A&A, 444 (2005) 51

7. EGRET on CGRO (Compton Gamma Ray Observ.)Data publicly available from NASA archive Instrumental parameters: Energy range: 0.02-30 GeV Energy resolution: ~20% Effective area: 1500 cm2 Angular resol.: <0.50 Data taking: 1991-1994 Main results: Catalogue of point sources Excess in diffuse gamma rays This talk: Excess consistent with DMA of 60 GeV WIMP in ALL sky directions Excess distribution explains peculiar shape of rotation curve (A&A, 444 (2005) 51)

8. π0 π0 WIMPS IC IC Brems Brems The EGRET excess of diffuse galactic gamma rays without and with DM annihilation Fit only KNOWN shapes of BG + DMA, i.e. 1 or 2 parameter fit NO GALACTIC models needed. Propagation of gammas straightforward If normalization free, only relative point-to-point errors of ≤7% important, not absolute normalization error of 15%. Statistical errors negligible.

9. Quarks from WIMPS Quarks in protons What about background shape? No SM No SM Protons Electrons Background from nuclear interactions (mainly p+p-> π0 + X ->  + X inverse Compton scattering (e-+  -> e- + ) Bremsstrahlung (e- + N -> e- +  + N) Shape of background KNOWN if Cosmic Ray spectra of p and e- known

10. Contribution from various hadronic processes PYTHIA processes: 11 f+f' -> f+f' (QCD) 2370 12 f+fbar -> f'+fbar' 0 13 f+fbar -> g + g 0 28 f+g -> f + g 2130 68 g+g -> g + g 1510 53 g+g -> f + fbar 20 92 Single diffractive (XB) 1670 93 Single diffractive (AX) 1600 94 Double diffractive 700 95 Low-pT scattering 0 Prompt photon production: 14 f+fbar -> g+γ 0 18 f+fbar -> γ +γ 0 29 f+g -> f +γ 1 115 g+g -> g + γ 0 114 g+g -> γ + γ 0 2 GeV 4 8 16 32 64 diff.

11. Background + signal describe EGRET data!

12. Analysis of EGRET Data in 6 sky directions C: outer Galaxy A: inner Galaxy B: outer disc Total 2 for all regions :28/36  Prob.= 0.8 Excess above background > 10σ. E: intermediate lat. F: galactic poles D: low latitude A: inner Galaxy (l=±300, |b|<50) B: Galactic plane avoiding A C: Outer Galaxy D: low latitude (10-200) E: intermediate lat. (20-600) F: Galactic poles (60-900)

13. bulge disk sun Fits for 180 instead of 6 regions 180 regions: 80in longitude  45 bins 4 bins in latitude  00<|b|<50 50<|b|<100 100<|b|<200 200<|b|<900  4x45=180 bins

14. Expected Profile Observed Profile z xy xy Rotation Curve 2002,Newberg et al. Ibata et al, Crane et al. Yanny et al. x y 1/r2 halo totalDM disk xz xz bulge Inner Ring Outer Ring 1/r2 profile and rings determined from inde-pendent directions Normalize to solar velocity of 220 km/s Dark Matter distribution v2M/r=cons. and (M/r)/r2 1/r2 for const. rotation curve Divergent for r=0? NFW1/r Isotherm const. Halo profile

15. Rotation curve of Milky Way Honma & Sofue (97) Schneider &Terzian (83) Brand & Blitz(93)

16. Do other galaxies have bumps in rotation curves? Sofue & Honma

17. Apocenter Pericenter Possible origin of ring like structure Infall of dwarf galaxy in gravitational potential of larger galaxy into elliptical orbit start precessions, if matter is not distributed homogeneous. Tidal forces  gradient of field, i.e.  1/r3. This means tidal disruption only effective at pericenter for large ellipticity! Could tidal disruption of dwarf galaxy lead to ringlike structure of 1010 solar masses? N-body simulations no clear answer. All depends on initial conditions. Also no clear explanation for ring of stars of 109 solar masses.

18. Tidal disruption of satellite in potential of larger galaxy Hayashi et al., astro-ph/02003004

19. H2 Inner Ring coincides with ring of dust and H2 -> gravitational potential well! 4 kpc coincides with ring of neutral hydrogen molecules! H+H->H2 in presence of dust-> grav. potential well at 4-5 kpc. Enhancement of inner (outer) ring over 1/r2 profile 6 (8). Mass in rings 0.3 (3)% of total DM

20. Astrophysicists: What is the origin of “GeV excess” of diffuse Galactic Gamma Rays? Astronomers: Why a change of slope in the galactic rotation curve at R0 ≈ 11 kpc? Why ring of stars at 14 kpc? Why ring of molecular hydrogen at 4 kpc? Cosmologists: How is DM annihilating?A: into quark pairs How is Cold Dark Matter distributed? Particle physicists: Is DM annihilating as expected in Supersymmetry? 7 Physics Questions answered SIMULTANEOUSLY if WIMP = thermal relic A: DM annihilation A: DM substructure A: standard profile + substructure A: Cross sections perfectly consistent with mSUGRA for light gauginos, heavy squarks/sleptons

21. 10 (wrong) objections against DMA interpretation • Proton spectra only measured locally. Spectra near center of • galaxy, where protons are accelerated, can be different and • produce harder gamma spectrum, as observed by EGRET. Answer: proton energy loss times larger than age of universe, so proton energy spectra will become equal by diffusion This is PROVEN by the fact that we see same spectrum and same excess in inner and outer galaxy. 2) Is background known well enough to make such strong statements? A: Background SHAPE is known, since mainly from pp collisions. Analysis does not depend on absolute fluxes from propagation models. Propagation.of gammas is straightforward. 3) Can unresolved point sources be responsible for excess? Answer: NO, if they have similar spectra as the many resolved point sources, they would reduce the data points at low energy, thus increasing the DMA contribution if shapes are fitted. Also do not expect 1/r2 profile for point sources.

22. 10 (wrong) objections against DMA interpretation 4) Does antiproton rate exclude interpretation of EGRET data? (L.B.) Bergstrom et al. astro-ph/0603632, Abstract: we investigate the viability of the model using the DarkSUSY package to compute the gamma-ray and antiproton fluxes. We are able to show that their (=WdB et al) model is excluded by a wide margin from the measured flux of antiprotons. • Problem with DarkSUSY (DS): • Flux of antiprotons/gamma in DarkSUSY: O(1) from DMA. • However, O(10-3) from LEP data • Reason: DS has diffusion box with isotropic diffusion -> • DMA fills up box with high density of antiprotons • 2) More realistic models have anisotropic diffusion. • E.g. spiral galaxies have magnetic fields perpendicular to • disk-> antiprotons may spiral quickly out of Galaxy.

23. Magnetic fields observed in spiral galaxies fieldline disk A few uG perpendicular to disc: Diffusion preferentially to disc? Alternativ: strong convection A few µG along spiral arms: Can lead to slow radial diffusion Isotropic diffusion assumes randomly oriented magnetic turbulences. Preferred magnetic field directions -> anisotropic diffusion

24. Preliminary results from GALPROP with isotropic and anisotropic propagation Antiprotons B/C ratio Summary: with anisotropic propagation you can send charged particles whereever you want and still be consistent with B/C and 10Be/9Be

25. Cosmic clocks: 10Be/9Be

26. EGRET EXCESS Statistical errors only Sofue &Honma R0=8.3 kpc v Inner rotation curve R0=7.0 Outer RC Black hole at centre: R0=8.00.4 kpc R/R0 10 (wrong) objections against DMA interpretation 5) Rotation curves in outer galaxy measured with different method than inner rotation curve. Can you combine? Also it depends on R0. Answer: first points of outer RC have same negative slope as inner RC so no problem with method. Change of slope seen for every R0. 6) Ringlike structures have enhanced density of hydrogen, so you expect excess of gamma radiation there. Why you need DMA? Answer: since we fit only the shapes of signal and BG, a higher gas density is automatically taken into account and DMA is needed to fit the spectral shape of the data. 7) Is EGRET data reliable enough to make such strong statements? Answer: EGRET spectrometer was calibrated in photon beam at SLAC. Calibration carefully monitored in space. Impossible to get calibration wrong in such a way that it fakes DMA.

27. 10 (wrong) objections against DMA interpretation 7) How can you be sure that this outer ring is from the tidal disruption of satellite galaxy, so one can expect DM there? Answer: one observes rings for all three ingredients of a galaxy: gas, stars and DM. The stars cannot be part of the disk, since the thickness of the ring is a factor 20 larger than the thickness of the disk. Furthermore, very small velocity dispersion of stars 8) Is it not peculiar that the rings are in the plane of the disk? Answer: the angular momenta of halo and disk tend to align after a certain time of precession, so rings end up in plane of the disk.. 9) The inner ring was not observed as a ring of stars. How can you be sure DM concentrates there? Answer: The density of stars and dust is to high to obtain substructure in the star population. However, the ring of dust and molecular hydrogen are proof of a graviational well, which indicates DM. 10) How can one reconstruct 3D halo profiles, if one observes gamma rays only along the line of sight without knowing the distance? Answer: if one observes in ALL directions, one can easily unfold, see rings of Saturn (same problem).

28. What about Supersymmetry?

29. Comparison with SUPERSYMMETRY Symmetry between FermionsBosons (Matter particles) (exchange particles) SUSY masses: 100 - 2000 GeV ! Lightest Supersymmetric Particle (LSP) is stable, heavy and weakly interacting  excellent Weakly Interacting Massive Particle (WIMP) DM candidate! R-Parity conservation: TWO SUSY particles at each vertex! LSP mostly photinolike in MSSM  DM = supersymmetric partner of CMB

30. EGRET? Cross sections for Direct DM detection in mSUGRA

31. Gauge unification perfect with SUSY spectrum from EGRET SM SUSY Update from Amaldi, dB, Fürstenau, PLB 260 1991 With SUSY spectrum from EGRET + WMAP data and start values of couplings from final LEP data perfect gauge coupling unification! Also b->s and g-2 in agreement with SUSY spectrum from EGRET

32. Summary EGRET excess shows that WIMP is thermal relic with expected annihilation into quark pairs DM becomes visible by gamma rays from fragmentation (30-40 gamma rays of few GeV pro annihilation from π0 decays) Results rather model independent, since only KNOWN spectral shapes of signal and background used, NO model dependent calculations of abs.fluxes. Different models or unknown experimental problems may change boost factor and/or WIMP mass, BUT NOT the distribution in the sky. SPATIAL DISTRIBUTION of annihilation signal is signature for DMA which clearly shows that EGRET excess is tracer of DM by fact that one can CONSTRUCT ROTATION CURVE FROM GAMMA RAYS. Conventional models CANNOT explain above points SIMULTANEOUSLY, especially spectrum of gamma rays in all directions, 1/r2 profile, shape of rotation curve, ring of stars at 14 kpc and ring of H2 at 4 kpc, ….