Indirect Evidence for Dark Matter from Galactic Gamma Rays

1. Indirect Evidence for DM from Galactic Gamma Rays • What is known about Dark Matter? • 23% of the Energy of the Universe • Weakly interacting Massive Partice (WIMP) • Annihilation with <σv>=2.10-26 cm3/s • Annihilation into Quarkpairs -> • Excess in galactic Gammarays (π0 decays) • Indeed observed by EGRET satellite • WIMP Mass 50-100 GeV from spectrum • Halo distribution of DM by observing in • many sky directions • Data consistent with Supersymmetry From CMB + SN1a + surveys if it is not dark, it does not matter

2. 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) !) Expansionrate 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.. Jungmann,Kamionkowski, Griest, PR 1995 Annihilation into lighter particles, like Quarks and Leptons -> 0’s -> Gammas! T=M/22 x=m/T

3.    f f f ~ f A Z    f f f   W Z 0    Z W DM Annihilation in Supersymmetry ≈37 gammas B-Fragmentation known -> Spectra of Positrons, Gammas and Antiprotons known! Dominant  +   A  b bbar quark pair Galaxy = Super B-Factory with rate 1040 x B-Factory

4. Gamma Spectra from WIMP Annihilation 60 GeV WIMP SPA1a’ WIMPS NN WIMPS NN IC IC IC Brems Bremsstr. Gamma Spectra for different decay channels Gamma Spectra with tau-decays dominant (m0 small) Gamma Spectra with b-fragmentation dominant (m0 large)

5. Quarks from WIMPS Quarks in protons What about background? 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

6. 2 Basics of astroparticle physics Gamma ray flux from WIMP annihilation in direction ψ: ρ=Mn Bl <2>/<>2  20-2000 Similar expressions for: pp->0+x->+x, ( = Gasdensity, max. in the disk) e->e, eN->eN, ( = Electron/Gamma density) Extragalactic background (isotropical) DM annihilation ( 1/r2 for flat rotationcurve) All have different energy spectra. Cross sections known. Densities less well known -> fit ONLY shapes with free normalization for background and signal Normalization error: 15% for EGRET. Point-to-point error 7%. Only latter important for shape fit

7. Clustering of DM -> boosts annihilation rate Annihilation  SQUARE of DM density Clumps with Mmin -> dominant contribution -> MANY clumps in given direction -> same boostfaktor in all directions Clustersize: ≈ Solarsystem? Mmin 10-8 -10-6 Mסּ? Steeply falling mass spectrum. Boost factor  <2>/<>2  20-2000

8. WIMP MASS 50 - 100 GeV Red=Flux of DM annihilation Yellow = background Blue = Uncertainty 0 WIMPS IC Extragal. Bremsstr. Background + signal describe EGRET data! 65 100 0 WIMPS IC Extragal. Bremsstr. Blue: background uncertainty Blue: WIMP mass uncertainty

9.  E-n n=2.5 2.7 n=3.0 Expl. of excess by T. Kamae et al, astro-ph/0410617

10. Analysis of EGRET Data in 6 sky directions C: outer Galaxy A: inner Galaxy B: outer disc 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)

11. Optimized Model from Strong et al. astro-ph/0406254 Change spectral shape of electrons AND protons C: outer Galaxy B: outer disc A: inner Galaxy π0 IC Brems E: intermediate lat. F: galactic poles D: low latitude 2 of optimized model:110/42  Prob. < 10-7

12. 300 MeV 150 MeV 100 MeV 500 MeV 1000 MeV 2000 MeV From orignal paper on Optimized Model Strong et al. astro-ph/0406254 longitude Real problem with conventional models: if data is perfectly fitted with sum of powerspectrum+monoenergetic peak for quarks, then you cannot get good fit with whatever powerspectrum you invent. In addition, DM has different spatial distribution, so fitting over all directions gives prob.<10-7 in all cases.

13. Quarks from WIMPS Quarks in protons What about background? 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

14. Fits for the “optimized” Model with DM C: outer Galaxy B: outer disc A: inner Galaxy E: intermediate lat. F: galactic poles D: low latitude 3 components: galactic background + extragalactic bg + DM annihilation fitted simultaneously with same WIMP mass and DM normalization in all directions. Boost factor around 20 in all directions and probability 0.8.

15. Expected Profile Observed Profile z xy xy Rotation Curve x y 1/r2 halo totalDM disk 2003, Ibata et al, Yanny et al. xz xz bulge Ghostly Ring: 108-109 Mvisible Matter 1010-1011 M Dark Matter (From Gamma Data: M=n m ) Total DM mass Galaxy: 3.1012M Inner Ring Outer Ring “Executive Summary” v2M/r=cons. and M/r3 1/r2 for const. rotation curve Divergent for r=0? NFW1/r Isotherm const. Halo profile

16. Do other galaxies have bumps in rotation curves? Sofue & Honma The DM mass of the outer ring is similar to the mass of the disk. Would the infall of such a heavy satellite galaxy destabilize disk? Answer: Many galaxies show RC with similar maxima and minima, which only can happen by ringlike structures, so the tidal disruption in successive orbits seems ok for stability..

17. From Eric Hayashi

18. H2 Fit results of halo parameters for 180 directions 14 kpc coincides with ring of stars at 14-18 kpc due to infall of dwarf galaxy (Yanny, Ibata, …..) 4 kpc coincides with ring of neutral hydrogen molecules! Forms 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 within R200 1/r2 profile and rings determined from inde-pendent directions

19. Longitude fits in plane of disk 0.1 < E < 0.5 GeV E > 0.5 GeV

20. m1/2 masses m0 Annihilation cross section in SUSY Squarks, sleptons heavy Charginos, neutralinos and gluinos light Spin ½ particles light (<500 GeV) Spin 0 particles heavy (≈TeV) Egret: WIMP 50-100 GeV WMAP: <σv>=2.10-26 cm3/s

21. 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 perfectly fitted with SUSY spectrum from EGRET

22. 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? Answer: Background shape is well known: mainly pp collisions for protons up to few 100 GeV. 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.

23. EGRET EXCESS Positrons Antiprotons Preliminary 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 4) Does antiproton rate exclude interpretation of EGRET data? (L.B.) Answer:Antiproton production: p+p->pbar+X: Npbar  <ρp2> Antiproton annihilation:p+pbar-> X:  <ρp3> <ρp3>/ <ρp>3 can be much larger than 1 by clustering 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.

24. 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. They 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).

25. Astrophysicists: What is the origin of “GeV excess” of diffuse Galactic Gamma Rays? Astronomers: Why a change of slope in the galactic rotation curve above R0=8.3 kpc? Why ring of stars at 14 kpc so stable? Why ring of molecular hydrogen at 4 kpc so stable? Cosmologists: How is Cold Dark Matter distributed? Particle physicists: Is DM annihilating as expected in Supersymmetry? 6 Physics Questions answered by this analysis A: DM annihilation A: DM substructure A: isothermal cored 1/r2 profile+subs. NFW excluded A: Cross sections perfectly consistent with SUSY

26. Summary EGRET excess can: 1) determine WIMP mass (50-100 GeV) 2) determine DM haloprofile 3) explain peculiar shape of rotation curve 4) statistical significance > 10 σ! 5) explain why excess has same shape in all directions Reconstruction of rotationcurve from GAMMA RAYS-> EGRET excess = Tracer of Dark Matter! Results practical model independent, since only KNOWN spectral shapes of signal and background are used, NOT model dependent calculations of absolute fluxes. Models WITHOUT DM cannot fit spectra in ALL directions and cannot explain the rotation curve nor stability of rings at 4 and 14 kpc.

27. Future Are results consistent with Supersymmetry? Answer: yes, for Squarks and Sleptons in TeV range WIMP is then bino like, i.e. in this case DM would be the SUSY partner of the CMB LHC Experiments will tell!

28. Future: Direct DM Searches Spin-dependent Spin-independent DAMA ZEPLIN Edelweiss CDMS ZEPLIN CDMS Edelweiss Projections Predictions from EGRET data assuming Supersymmetry

29. SUPERSYMMETRIC DARK MATTER AND THE EXTRAGALACTIC GAMMA RAY BACKGROUND 2/d.o.f=10.9/6  P=0.1 2/d.o.f=4.7/4  P=0.3 m =50 GeV W. de Boer et al., Comment to PRL D. Elssässer and K. Mannheim, Phys.Rev.Lett.94:171302,2005

30. Positron fraction and antiprotons from present balloon exp. Positrons Antiprotons Signal Signal Background Background Positrons Antiprotons Antiproton production: p+p->pbar+X: Npbar  <ρp2> Antiproton annihilation: p+pbar-> X:  <ρp3> <ρp3>/ <ρp>3 can be much larger than 1 by clustering of gas, thus boosting the annihilation SAME Halo and WIMP parameters as for GAMMA RAYS but fluxes dependent on propagation! DMA can be used to tune models: at present no convection, nor anisotropic diffusion in spiral arms.

31. Fits for 180 instead of 6 regions 180 regions: 80in long. 45 bins 4 bins in latitude  00<|b|<50 50<|b|<100 100<|b|<200 200<|b|<900  4x45=180 bins

32. Objections from astrophysicists Astrophysicists:cannot believe collisionless DM, i.e. particles which experience only gravity, is self-annihilating and that particle physicists even believe to know spectral shapes of final states! They prefer their “optimized” models or “local bubbles”. Answer: too bad, but their “local bubbles” or “optimized models” do not work if they learn how to handle correlated errors.

33. Objections from particle physicists Particle physicists: you assume spectrum of protons to be the same everywhere in galaxy. How can you be sure? Answers: 1) If centre of galaxy would be different because of SN there is no reason to get same shape of excess in outer galaxy (very few SN) 2) energy loss times > age of universe, very hard to image strong changes in spectral shape if protons diffuse from centre to us in  108 yr

34. Sofue &Honma R0=8.3 kpc Answer: First points of outer rot. curve in perfect agreement with inner rot. curve. CHANGE in slope for any R0 R0=7.0 v Inner rotation curve Outer rotation curve Black hole at centre: R0=8.00.4 kpc R/R0 Objections from astronomers Astronomers: outer rotation curve determined with different method than inner rotation curve. Hard to compare. Furthermore slope depends on distance to centre (R0)

35. Shape of excess in all directions the same! Egret Excess above extrapolated background from data below 0.5 GeV Statistical errors only Excess same shape in all regions implying same source everywhere Important: if experiment measures gamma rays down to 0.1 GeV, then normalizations of DM annihilation and background can both be left free, so one is not sensitive to abso- lute background estimates, BUT ONLY TO THE SHAPE, which is much better known.

36. The Big Bangand its particles Gamma spectra for BG + DMA (Pythia, Sjöstrand) Rotation curve Doughnut of stars at 14 kpc Doughnut of H2 at 4 kpc Astronomers Cosmics Gammas (Galprop, Moskalenko & Strong) Astrophysics 23%DM, Hubble Annihilation Cross section Galaxy formation Cosmology Particle Physics Big Bang

37. Optimized Model from Strong et al. astro-ph/0406254 Change spectral shape of electrons AND protons Protons Electrons Nucleon and electron spectra tuned to fit gamma ray data. Apart from the difficulty to have inhomogeneous nuclei spectra (SMALL energy losses!) the model does NOT describe the spectrum IN ALL DIRECTIONS! B/C

38. Optimized Model from Strong et al. astro-ph/0406254 Change spectral shape of electrons AND protons

39. Optimized Model from Strong et al. astro-ph/0406254 Change spectral shape of electrons AND protons 300 MeV 150 MeV 100 MeV 500 MeV 1000 MeV 2000 MeV

40. Energy loss times of electrons and nuclei t-1 = 1/E dE/dt Electrons & Positrons Nucleons univ Bremsstrahlung Ionization Ionization IC, synchrotron Coulomb 107 yr Coulomb 106 yr 107 yr 1 TeV 1 GeV 1 GeV 1 TeV Ekin, GeV/nucleon Ekin, GeV Nucleon energy loss timescale: 1 GeV: ~1010 yr 1 TeV: ~1012 yr Very difficult to get Ekin=F(R) Electron energy loss timescale: 1 GeV: ~5.108 yr 100 TeV: ~3 000 yr

41. EGRET on CGRO (Compton Gamma Ray Observ.) 9 yrs of data taken (1991-2000) Main purpose: sky map of point sources above diffuse BG.

42. N-body Simulation der Formation einer Galaxie Clustering enhances flux from DMA by factor 20-2000 (Dokuchaev et al.) Movie from M. Steinmetz, Potsdam

43. Apocenter Pericenter Possible origin of ring like structure Infall of dwarf galaxy in gravitational potential of larger galaxy into elliptical orbit starts precession Tidal forces  gradient of field, i.e.  1/r3. This means tidal disruption only effective at pericentre for large ellipticity! -> ringlike structures of gas, stars and Dark Matter! • These are indeed observed at 14 kpc: • ring of atomic hydrogen • “ghostly” ring of old stars • Discovered in 2003 by SDSS • (109 solar masses!) • 3) ring of enhanced gamma radiation • (discovered in 1997, called cosmological enhancement factor) • That it corresponds to DMA • spectrum, only now..)

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

45. 2  1/r2 2 toroidal Rings Determination of the halo profile DM Gamma Fluss: Berezinsky, Dokuchaev, Eroshenko Boost Factor  <2>/<>2  20-2000 =2 =2

46. Fit results of halo parameters (<v> from WMAP) Parameter values: 180 independent sky directions i.e. ca. 1400 independent data points. only 12 free parameters. Outer ring: mainly from galactic anticenter Inner ring: mainly from galactic center Triaxial Halo: mainly from outside disc 4 kpc Boostfactor  20 for “optimized” model, 100 for “conventional” model for WIMP=65 GeV. Larger for smaller WIMP mass Dokuchaev et al: 10<B<2000, IDM2004 Sun 8 kpc 14 kpc

47. HI at 14 kpc Cosmic Enhancement Factor H2 at 4 kpc Rings of DM observed by EGRET before!

48. This analysis Mdisc/Mhalo Concentration Mhalo Mhalo Galactic Parameters Further parameters: R200=295 kpc DM: 3.1012 Mסּ Baryonic: 6.1010 Mסּ Mass of outer (inner) ring 3 (0.3)% of total DM. Only so important, while nearby!! (For dwarf at 14 kpc: visible/DM0.02)

49.  E-n n=2.5 2.7 n=3.0 Expl. of excess by T. Kamae et al, astro-ph/0410617

50. Background uncertainties T. Kamae et al, 2004, astro-ph/0410617 III=double break III II Main results on halo profile, substructure, and WIMP mass not affected after renormalization to data between 0.1 and 0.5 GeV. Note: point-to-point errors only half of plotted errors of 15%. Statistical errors negligible. BG I