Excess of EGRET Galactic Gamma Ray Data interpreted as Dark Matter Annihilation

Size: px

Start display at page:

Download "Excess of EGRET Galactic Gamma Ray Data interpreted as Dark Matter Annihilation"

Joel Powell
5 years ago
Views:

1 Excess of EGRET Galactic Gamma Ray Data interpreted as Dark Matter Annihilation Wim de Boer, Marc Herold, Christian Sander, Valery Zhukov Univ. Karlsruhe Alex Gladyshev, Dmitri Kazakov Dubna Outline (see astro-ph/ ) EGRET Data on diffuse Gamma Rays shows excess in all sky directions with the SAME spectrum Halo parameters from sky map WIMP mass from spectrum Data consistent with Supersymmetry September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 1

2 Physics Problems Cosmologists: What is CDM and Dark Energy made of? Particle physicists: Where are the Supersymmetric Particles? Astrophysicists: What is the origin of excess of diffuse Galactic Gamma Rays? Astronomers: Why a change of slope in the galactic rotation curve above R 0 =8.5 kpc? Why ring of stars at 14 kpc so stable? Why ring of molecular hydrogen at 4 kpc so stable? September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 2

3 Proposed Solution DM made of WIMPS annihilating into quarks, which yield hard gammas from π 0 decays Annihilation cross section given by HUBBLE constant! Gamma excess correlated with ring of stars at kpc thought to originate from infall of a dwarf galaxy and ring of DM at 4 kpc correlated with molecular H 2 From SPECTRUM of excess of gamma rays DM: WIMP mass GeV From INTENSITY: halo distribution and rotation curve WIMP has properties of supersymmetric lightest particle September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 3

4 Executive Summary Expected Profile Observed Profile z xy xz xy Isothermal Profile v 2 M/r=cons. and xz ρ M/r 3 ρ 1/r 2 for const. rotation curve Rotation Curve Rotation Curve x y DM halo disk 2003, Ibata et al, Yanny et al. disk bulge Inner Inner Ring Ring F R F G Outer Ring Outer Ring Halo profile September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 4

5 Hubble const. determines WIMP annihilation x-section Thermal equilibrium abundance Jungmann,Kamionkowski, Griest, PR 1995 Comoving number density Actual abundance T=M/25 x=m/t Boltzmann equation: H-Term takes care of decrease in density by expansion. Right-hand side: Annihilation and Production. T>>M: f+f->m+m; M+M->f+f T<M: M+M->f+f T=M/25: M decoupled, stable density (wenn annihilation rate expansion rate, i.e. Γ=<σv>nχ H!) WIMP annihilation is a strong source of antiprotons, positrons and gammas by annihilation into quarks. Present number density (Ωh 2 =0.113±0.009)requires <σv>= cm 3 /s assuming no coannihilation September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 5

6 Neutralino Annihilation Final States χ χ ~ f f f χ χ f f χ χ f f χ χ χ W χ ± χ 0 W χ Z Z Dominant Diagram for WMAP cross section: χ + χ A b bbar quark pair B-fragmentation well studied at LEP! Yield and spectra of positrons, gammas and antiprotons well known! September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 6

7 10-27 Annihilation cross sections in m 0 -m 1/2 plane (µ > 0, A 0 =0) tan=5 tan=50 bb t t bb t t EGRET WMAP ττ WW ττ WW For WMAP x-section of <σv> cm 3 /s one needs large tanβ in bulk region (no coannihilation, no resonances) September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 7

and EGRET simultaneously, if DM is neutralino with mass in range 50-100 GeV and squarks and

8 EGRET excess interpreted as DM consistent with WMAP, Supergravity and electroweak constraints 0 Stau coannihilation m A resonance MSUGRA can fulfill all constraints from WMAP, LEP, b->sγ, g-2 and EGRET simultaneously, if DM is neutralino with mass in range GeV and squarks and sleptons are O(1 TeV) WMAP Bulk EGRET September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 8

Excess of Diffuse Gamma Rays above 1 GeV as measured by EGRET satellite (9 yrs of data) Strong, Moskalenko, Reimer, to be published A B C Inv. Compton Bremsstrahlung Prel.

9 Excess of Diffuse Gamma Rays above 1 GeV as measured by EGRET satellite (9 yrs of data) Strong, Moskalenko, Reimer, to be published A B C Inv. Compton Bremsstrahlung Prel. π 0 D E F A: inner Galaxy (l=±30 0, b <5 0 ) B: Galactic plane avoiding A C: Outer Galaxy D: low latitude ( ) E: intermediate lat. ( ) F: Galactic poles ( ) September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 9

10 Local electron and proton spectra determine shape of gamma background No SM No SM Protons Electrons WIMPS Solar modulation (SM) important below 10 GeV Proton and electron spectra above 10 GeV well measured Gamma spectrum well known, unless one assumes local bubble, i.e. spectra in galaxy different from locally measured ones. September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 10

Excess of Diffuse Gamma Rays has same spectrum in all directions compatible with WIMP mass of 50-100 GeV Important: if experiment measures gamma rays down to 0.

11 Excess of Diffuse Gamma Rays has same spectrum in all directions compatible with WIMP mass of GeV Important: if experiment measures gamma rays down to 0.1 GeV, then normalizations of DM annihihilation and background can both be left free, so one is not sensitive to absolute background estimates, BUT ONLY TO THE SHAPE, which is much better known. September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 11

12 Diffuse Gamma Rays for different sky regions A B C D E F DMA Boostfactor <ρ 2 > If boost factor, i.e. clustering, similar in all directions, then signal strength determines DM density ρ September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 12

13 Why LIGHT traces DM in disc Reasons for enhanced DM in disc of galaxy: 1) Adiabatic compression of halo by gravity from disc (Blumenthal, Kalnajs, Wilkinson,..) (halo distribution may be modified by resonant interactions between bar and halo, Athanassoula, Katz, Weinberg,..) 2) Anisotropic infall along filaments of DM (e.g. ring of stars at kpc thought to originate from infall of dwarf galaxy (Yanny et al., Ibata et al., ) Parametrize with at least 2 rings: Inner ring for 1) Outer ring for 2) September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 13

14 Fit results of halo parameters Gamma Ray Flux: (<σv> from WMAP) Halo Parameters: (assuming boost fct B l same in all directions, comes out B> 20) Dokuchaev et al: 10<B<100, IDM rings with maximum intensity at 4 and 14 kpc Enhancement over isothermal profile 3 and 8, respectively Sensitive to radius, because Sun OFF CENTER! H 2 H 4 R [kpc] 14 kpc coincides with ring of stars at kpc due to infall of dwarf galaxy (Yanny, Ibata,..) 4 kpc coincides with ring of neutral hydrogen molecules! September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 14

15 Halo profiles Isothermal cored profile NFW cuspy profile WITHOUT rings WITH rings WITHOUT rings WITH rings α,β,γ=2,2,0 α,β,γ=1,3,1 September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 15

16 Longitude fits for isothermal (cored) profile WITHOUT rings WITH 2 rings DISC 10 0 <b<20 0 DISC 10 0 <b< <b< <b< <b< <b<90 0 Halo parameters from fit to 180 sky directions: 4 long. profiles for latitudes <5 0, 5 0 <b<10 0, 10 0 <b<20 0, 20 0 <b<90 0 (=4x45=180 directions) September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 16

17 Latitude fits for isoth. profile with long <30 0 below 500 MeV above 500 MeV September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 17

18 Fit with outer ring only in observable star region 0.1 < Eγ < 0.5 GeV Eγ > 0.5 GeV Stars only observed in galactic anticentre EGRET data requires complete ring of DM, not only in region where stars observed September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 18

19 EGRET data compatible with prolate isothermal halo profile with b/a 0.9, c/a 0.8 W. de Boer et al., astro-ph/ (α,β,γ) define the slope ρ 0 - local density GeV/cm 3 a -scale parameter (depends on ρ 0 ) Isothermal profile: α,β,γ,a = 2,2,0,4 NFW cusp Isothermal core Preferred structure (Bailin, Steinmetz,astro-ph/ z y b a x c Ellipsoid: x 2 /a 2 +y 2 /b 2 + z 2 /c 2 = c September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 19

20 M disc /M halo Galactic Parameters NFW Concentration NFW: halo too massive compared with EGRET data Galactic parameters from EGRET data M disc /M halo M halo isothermal Concentration M halo M halo M halo Isothermal profile: perfectly compatible with EGRET data Further parameters: R 200 =295 kpc סּM DM: סּM Baryonic: Mass of outer (inner) ring <3 (1)% of total DM. Only so important, while nearby!!!!!!!!! September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 20

21 Rotation curve of our galaxy Rotation Curve disk bulge DM halo Inner Ring Outer Ring F R F G סּM Rotation curve shows there is a ring of CDM with a mass of a few September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 21

22 Local surface density Σ Height distribution and velocity dispersion σ of local stars determine local gravitational potential (just like decrease in atmospheric density is determined by gravity of earth). Decrease in rotation curve suggests little Dark Matter. First measurements: Jan Oort in 1932: assuming constant σ: repulsive gravity. Later: σ(z ) E.g. Σ= ρdz = 71±6 Mסּ/pc -2 for z max =1.1 kpc by Kuijken+ Gilmore, They assumed constant DM density and very little of it. So they were stretching visible matter by brown dwarfs etc. 2001: Olling +Merrifield: consensus value of Σ from visible matter: 35± : Bienayme et al.: Σ = 85±? Error strongly dependent on assumptions of DM distributions. 2004: de Boer et al.: Σ DM =60 Σ baryonic =30 Mסּ/pc -2 with steeply varying DM density steep function of z (on slope of ring!) September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 22

23 SUSY Mass spectra in msugra LSP largely Bino DM may be supersymmetric partner of CMB Charginos, neutralinos and gluinos light September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 23

24 Supersymmetry at linear collider Karl Ecklund, Cornell pb x-section! September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 24

25 Supersymmetry at proton collider Typical cross-sections (pb) Silke Duensing m [GeV] pb x-section with very little background! September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 25

26 Comparison with direct DM Searches Predictions from EGRET data September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 26

27 Summary The excess of EGRET diffuse galactic gamma rays in the range between 1 and 100 GeV shows all the key features from WIMP annihilation: 1) the energy spectrum of the excess is the same in all sky directions and is consistent with the π 0 decays from monoenergetic quarks originating from WIMP annihilation for a WIMP mass between GeV 2) the intensity distribution of is used to determine the halo profile, which, outside the plane of the galaxy, was found to correspond to an isothermal (cored) profile and excludes the cuspy NFW profile 3) in the plane of the galaxy the excess shows strong substructure: two oval rings at radii of 4 and 14 kpc (correlated with ring of molecular hydrogen at 4 kpc and ring of stars at 14 kpc) 4) these rings yield a change of slope at R=R 0 in the rotation curve and are consistent with the high local surface density 5) all features and cross sections are consistent with the WIMP being the neutralino from Minimal Supersymmetry 6) Alternative conventional models cannot explain stability of ring of stars at 14 kpc and H 2 ring of molecular gas at 4 kpc, nor change of slope in rotation curve, nor halo shape of excess September 9, 2004 IDM2004, Edinburgh, W. de Boer, Univ. Karlsruhe 27

EGRET excess of diffuse Galactic Gamma Rays interpreted as Dark Matter Annihilation

EGRET excess of diffuse Galactic Gamma Rays interpreted as Dark Matter Annihilation Wim de Boer, Christian Sander, Valery Zhukov Univ. Karlsruhe From CMB + SN1a + Dmitri Kazakov, Alex Gladyshev structure