We don ’t know it, because we don’t see it!

W. de Boer, Univ. Karlsruhe

WHEPP-9,Bhubaneswar, Jan. 10, 2006 1

We don’t know it,because we don’t see it!

Do Gamma Rays reveal the DM of our Galaxy?

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



• What is known about Dark Matter?

23% of the Energy of the Universe IF THERMAL RELIC THEN IT MUST BE Weakly interacting Massive Particle (WIMP) Annihilation with <σv>=2.10-26 cm3/s

• Annihilation into Quarkpairs -> Excess in galactic Gamma rays (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

DM halo profile of galaxycluster from weak lensing

Do Gamma Rays reveal the DM of our Galaxy?



Problems solvedby DM

Annihilation

Where are signalsfrom DM annihilation?Consistent with Supersymmetry?

Particle Physics

Cosmology

Astro-particle Physics

23%DM, Hubble-> DM Annih. x-sect.How does DM annihilate? How isDM distributed?

Excess ofGamma rays

Astronomy

Structure inRotation curve“Doughnut” of starsat 14 kpc“Doughnut” of dustand H2 at 4 kpc



What does it imply: DM is thermal relic?Answer: low number density (like for

baryons) means DM annihilated away (like

baryons)Thermal equilibrium abundance

Actual abundance

T=M/22Co

mo

vin

g n

um

ber

d

ensi

ty

x=m/TJungmann,Kamionkowski, Griest, PR 1995

WMAP -> h2=0.1130.009 -> <v>=2.10-26 cm3/s

DM increases in Galaxies:1 WIMP/coffee cup 105 <ρ>. DMA (ρ2) restarts again..

T>>M: f+f->M+M; M+M->f+fT<M: M+M->f+fT=M/22: M decoupled, stable density(when Annihilationrate Expansion- rate, i.e. =<v>n(xfr) H(xfr) !)

Annihilation into lighter particles, likeQuarks and Leptons -> 0’s -> Gammas!Only assumption in this analysis:WIMP = THERMAL RELIC!



DM Annihilation in Supersymmetry

Dominant + A b bbar quark pair

B-Fragmentation known!Hence Spectra of Positrons,Gammas and Antiprotons known!

f

f

f

f

f

f

Z

Z

W

W 0

f~

h,A Z

Galaxy = Super B-Fabrik with rate 1040 x B-Factory

≈37 gammas



EGRET on CGRO (Compton Gamma Ray Observ.)

9 yrs of data taken in space! (1991-2000)



The EGRET excess of diffuse galactic gamma rays without and with DM annihilation

π0π0

WIM

PS

IC

Brems

IC

Brems

If normalization free, only relative point-to-point errors of ≤7% important, not absolute normalization error of 15%. Statistical errors negligible.

Fit only KNOWN shapes of BG + DMA, i.e. 1 or 2 parameter fitNO GALACTIC models needed. Propagation of gammas straightforward



No SM

Electrons

No SM

Protons

Quarks fromWIMPS

Quarks in protons

What about background shape?

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



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 213068 g+g -> g + g 151053 g+g -> f + fbar 20 92 Single diffractive (XB) 1670 93 Single diffractive (AX) 1600 94 Double diffractive 70095 Low-pT scattering 0Prompt photon production:14 f+fbar -> g+γ 018 f+fbar -> γ +γ 029 f+g -> f +γ 1115 g+g -> g + γ 0114 g+g -> γ + γ 0

Contribution from various hadronic processes

2 GeV4

816

3264

diff.



Background + signal describe EGRET data!

Blue: background uncertainty

Background + DMA signal describe EGRET data!

Blue: WI MP mass uncertainty

50 GeV

70

I CI C



Analysis of EGRET Data in 6 sky directions

A: inner Galaxy (l=±300, |b|<50)B: Galactic plane avoiding AC: Outer Galaxy

D: low latitude (10-200)

E: intermediate lat. (20-600)F: Galactic poles (60-900)

A: inner Galaxy B: outer disc C: outer Galaxy

D: low latitude E: intermediate lat. F: galactic poles

Total 2 for all regions :28/36 Prob.= 0.8 Excess above background > 10σ.



Conventional Model without DMA in 6 sky regions

2 of conventional model:663/42 Prob. = 0



Fits for 180 instead of 6 regions

180 regions:80 in long. 45 bins4 bins in latitude 00<|b|<50 50<|b|<100

100<|b|<200

200<|b|<900

4x45=180 bins

bulge disk

sun



x y

z

2002,Newberg et al. Ibata et al, Crane et al. Yanny et al.

1/r2 profile and ringsdetermined from inde-pendent directions

Outer Ring

Inner Ring

bulge

tota

lDM

1/r2 halodisk

Rotation Curve

Normalize to solar velocity of 220 km/s

xy

xz

Expected Profile

v2M/r=cons.and

(M/r)/r2

1/r2

for const.rotation

curveDivergent for

r=0?NFW1/r

Isotherm const.

Dark Matter distribution

Halo profile

Observed Profile

xy

xz



Honma & Sofue (97)Schneider &Terzian (83)Brand & Blitz(93)

Rotation curve of Milky Way



Do other galaxies have bumps in rotation curves?

Sofue & Honma



Possible origin of ring like structure

Infall of dwarf galaxy in gravitational potential of larger galaxyinto elliptical orbit start precessions, if matter is notdistributed homogeneous.

Tidal forces gradient of field, i.e. 1/r3. This meanstidal disruption only effective at pericenter for large ellipticity!

Apocenter

Pericenter

Could tidal disruption of dwarf galaxy lead to ringlike structure of 1010 solar masses?

N-body simulations no clearanswer. All depends oninitial conditions. Also no clear explanation for ring ofstars of 109 solar masses.



Tidal disruption of satellite in potential of larger galaxy

Hayashi et al.,astro-ph/02003004


WHEPP-9,Bhubaneswar, Jan. 10, 2006 19From Eric Hayashi

Tidal forces1/r3 disruptionmostly at pericenter

enhancementof DM at pericenter



Enhancement of inner (outer) ring over 1/r2 profile 6 (8).Mass in rings 0.3 (3)% of total DM

Inner Ring coincides with ring of dust and H2 -> gravitational potential well!

H2

4 kpc coincides with ring ofneutral hydrogen molecules!Forms in presence of dust->grav. potential well at 4-5 kpc.



Haloprofile without rings



Haloprofile with rings



Determination of halo profile

DM Gamma Flux:

=2

1/r2 2 toroidal Rings

Berezinsky, Dokuchaev, EroshenkoBoost Factor <2>/<>2 20-2000

2

=2



Clustering of DM -> boosts annihilation rate

Clumps with Mmin -> dominantcontribution -> MANY clumps in given direction -> same boostfaktor in all directions

Annihilation SQUARE of DM density

Clustersize: ≈ Solarsystem?Mmin 10-8 -10-6 Mּס?Steeply falling mass spectrum. Boost factor <2>/<>2 20-2000From fit: B≈100 for WIMP of 60 GeV



10 (wrong) objections against DMA interpretation

1) 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.Signature is not only excess, BUT SPATIAL DISTRIBUTION OF EXCESS AS 1/r2 profile+substr.

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.




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.

4) Does antiproton rate exclude interpretation of EGRET data? (L.B.)

Answer:Antiproton production: p+p->pbar+X: Npbar <ρCR ρGas > Antiproton annihilation:p+pbar-> X: <ρGas

2> <ρGas

2>/ <ρGas>2 can be much larger than 1 by clustering

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.

R0=8.3 kpc

R0=7.0v

R/R0

Innerrotationcurve

Outer RC

Black hole at centre: R0=8.00.4 kpc

Sofue &Honma

AntiprotonsPositrons

PreliminaryStatistical errors only

EGRET EXCESS




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).



What

about

Supersymmetry?



Allowed mSUGRA region

A0=0tb=50

What about WMAP? Not used sofar. Large tanβ≈50->WMAP ok.

LHC:light gauginoseasily observable



Gauge unification perfect with SUSY spectrum from EGRET

With SUSY spectrum from EGRET + WMAP data and start values of couplings from final LEP data perfect gauge coupling unification!

Up

date

fro

m A

mald

i,

dB

, F

ürs

ten

au

, P

LB

260

1991

SM SUSY

Also b->s and g-2 in agreement with SUSY spectrum from EGRET



7 Physics Questions answered SIMULTANEOUSLY by this analysis

• 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?

A: DM substructure

A: DM annihilation

A: isothermal coredprofile+substructure

A: Cross sections perfectly consistent with mSUGRA for light gauginos, heavy squarks/sleptons



Astrophysics solution: Optimize e,p spectra to fit gammas “Optimized Model” from Strong et al. astro-ph/0406254

Nucleon and electron spectratuned to fit gamma ray data.

Have to assume we live in localBubble. Production of secondarynuclei not described.with sameparameters. BUT gamma raysnot well described either!

Electrons Protons

B/C



2 of optimized model:110/42 Prob. < 10-7

A: inner Galaxy B: outer disc C: outer Galaxy

D: low latitude E: intermediate lat. F: galactic poles

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

π 0IC

Brems



From original paper on Optimized Model Strong et al. astro-ph/0406254

100 MeV 150 MeV 300 MeV

500 MeV 1000 MeV

2000 MeV

Real problem with conventional models: if data is perfectly fitted with sum of power spectrum+monoenergetic peak for quarks, then you cannot get good fitwith whatever power spectrum you invent. In addition, DM has different spatial distribution, so fitting over all directions gives prob.<10-7 in all cases.

longitude



Summary

10σ EGRET excess shows all key features from DM annihilation:

Excess has same shape in all sky directions: everywhere it is perfectly (only?) explainable with superposition of background AND mono-energetic quarks of 50-100 GeV Results consistent with minimal SUPERSYMMETRY

Excess is TRACER OF DM, since it can explain peculiar shape of rotation curve

Excess follows expectations from galaxy formation: cored 1/r2 profile with substructure, visible matter/DM0.02

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, ….

Results model independent, since only KNOWN spectral shapes of signal and background used, NO model dependent calculations of absolute fluxes.

Significance >10σ with >1400 indep. data points



Future: Accelerators

Are results consistent with Supersymmetry?

LHC/ILC Experiments will tell!

Answer: yes, for Squarks and Sleptons in TeV range WIMP is then bino like, i.e. in this case



EGRET?

Cross sections for Direct DM detection



Ring of enhanced gamma radiation observed by EGRET before!

H2 at 4 kpc

HI at 14 kpc CosmicEnhancementFactor



Fit results of Halo Parameter

(<v> from WMAP)Parameter values:

Boostfactor 20 for “optimized” model, 100 for “conventional” model for WIMP=65 GeV.

Larger for smaller WIMP massDokuchaev et al: 10<B<2000, IDM2004

180 independent sky directionsi.e. ca. 1400 independent datapoints. only 12 free parameters.

Outer ring: mainly from galactic anticenterInner ring: mainly from galactic centerTriaxial Halo: mainly from outside disc

4 kpc

14 kpcSun8 kpc



Halo density on scale of 300 kpc

Sideview Topview

Cored isothermal profile with scale 4 kpc Total mass: 3.1012 solar masses



Halo density on scale of 30 kpc

Sideview Topview



Annihilation cross sectionsin m0-m1/2 plane (μ > 0, A0=0)

tan=5 tan=50bb t t

WW

bb t t

WW

For WMAP x-section of <v>2.10-26 cm3/s one needs large tanβ

10-2410-27

EGRETWMAP

squa

rksneutralinos



EGRET Point:

BULK region

NO Coannilation

Dominant: A-exchange

tan β dependence of relic density

We don ’t know it, because we don’t see it!

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