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Can the WMAP haze really be a signature of annihilating neutralino dark matter?

Can the WMAP haze really be a signature of annihilating neutralino dark matter?. Daniel Cumberbatch (CWRU), Joe Zuntz (Oxford), Joe Silk (Oxford) and Hans Kristian Kamfjord Eriksen (Oslo). arXiv:0902.0039. Wilkinson Microwave Anisotropy Probe (WMAP). Cosmic Microwave Background (CMB)

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Can the WMAP haze really be a signature of annihilating neutralino dark matter?

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  1. Can the WMAP haze really be a signature of annihilating neutralino dark matter? Daniel Cumberbatch (CWRU), Joe Zuntz (Oxford), Joe Silk (Oxford) and Hans Kristian Kamfjord Eriksen (Oslo) arXiv:0902.0039 CWRU, February 2009

  2. Wilkinson Microwave Anisotropy Probe (WMAP) • Cosmic Microwave Background (CMB) • Temperature anisotropies • Polarization anisotropies • Cosmological parameter estimation • Galactic Foregrounds • Requires estimation before CMB signal extraction • Multiple sources • Dominant foregrounds: • Free-Free (Thermal Bremsstrahlung) • Thermal Dust • Synchrotron • Minimized in WMAP range (23 <  < 94 GHz) CWRU, February 2009

  3. WMAP Haze • Excess Free-Free emission from hot gas (T~105 K) • Gas thermally unstable • Insufficient gas abundance at 104 K (recombination lines) or 106 K (X-rays). • Exotic Sources of synchrotron emission • Ultra-relativistic electrons from supernovae • Dark Matter annihilation • SUSY neutralinos (Hooper ‘07) • Exciting DM (XDM) (Weiner ‘08) • Compact Composite Objects (CCO’s) (Zhitnitsky ‘08) • Sommerfeld-enhanced DM (Lattanzi ‘08) CWRU, February 2009

  4. Foregrounds: Free-Free • Free-Free (or thermal Bremsstrahlung) emission • Coulomb interactions between free e-and hot interstellar gas • Maps of H recombination line emission  EM •  H maps can trace morphology of Free-Free emission • Wisconsin H Mapper (WHAM) • Southern H Sky Survey Atlas (SHASSA) • Virginia Tech Spectral-Line Survey (VTSS) CWRU, February 2009 CWRU, February 2009

  5. Foregrounds: Free-Free • Correct H map for dust-extinction • assume uniform mixing of warm gas and dust • in E(B-V) magnitudes • Mask out regions A(H)=2.65E(B-V)>1 CWRU, February 2009

  6. Foregrounds: Dust • Thermal dust emission • Microscopic dust grains vibrating in thermal equilibrium with ambient radiation field • Finkbeiner Davis and Schlegel (FDS) @ 94 GHz may also trace electric dipole emission from smallest dust grains • Excited into rotational modes by collisions with ions CWRU, February 2009

  7. Foregrounds: Synchrotron • Mainly from e- near supernovae explosions • Shock-accelerated to relativistic (i.e. >MeV) energies • Subsequently lose energy from ICS (Starlight or CMB) and Synchrotron emission (Galactic Magnetic Field) • Measured best at v <1 GHz • Full-sky map at 408 MHz (Haslam et al.) CWRU, February 2009

  8. Template Fitting Solve Matrix Equation: Pa = w CWRU, February 2009

  9. Template Fitting • P ≠square • P ≠ linearly independent rows P ≠invertible by solving for pseudoinverseP+  Minimise CWRU, February 2009

  10. 3-template fit • Nside=64 • Beam Width=3 Determined by Gibbs Sampling • Multi-linear regression of free-free, dust and synchrotron templates r=Pa-w Unwanted sources • Residual Map  (Gibbs) (ILC) CWRU, February 2009

  11. 3-template fit  Remove point sources, re-fit … (K-Band) (Ka-Band) (Q-Band) CWRU, February 2009

  12. 3-template fit  2>1 significant Introduce 2: (Q-Band) (K-Band) (Ka-Band) 2K = 5.54 (6.59), 2Ka = 0.88 (1.45), 2Q = 1.08 (2.12) [Full-Sky] 2K = 14.69 (16.59), 2Ka = 1.65 (2.42), 2Q = 1.60 (2.84) [< 50] CWRU, February 2009

  13. 3-template fit • Using ratios of elements of a CWRU, February 2009

  14. 3-template fit • Correlation Matrix:  Haze is correlated with Synchrotron Emission CWRU, February 2009

  15. 3-template fit  Haze is statistically significant < 50 around GC  Haze is correlated with Synchrotron emission • Exotic component (e.g. Dark Matter) ??? • If so, would expect <50° ≠ >50°k  Allow for spatial variation in sync. by using multiple templates…  = 50 CWRU, February 2009

  16. 4-template fit  Minimise 2red. w.r.t.  using two Synchrotron templates (Gibbs) (ILC) CWRU, February 2009

  17. 4-template fit (Q-Band) (K-Band) (Ka-Band) ∆2K(%)=20.0 (18.7), ∆2Ka(%)=7.7 (6.8), ∆2Q(%)=6.3 (4.9) [FS] ∆2K(%)=46.0(45.5), ∆2Ka(%)=24.8(24.9), ∆2Q(%)=25.2(22.0) [<50] CWRU, February 2009

  18. 4-template fit • Using ratios of elements of a for synchrotron components CWRU, February 2009

  19. Dark Matter • WIMP DM candidates annihilate to e+/- +…other SM particles • DM annihilation Rate (r)2 hence increases towards GC e+/-propagate ISM e+/-interact with galactic magnetic field e+/-radiate via synchrotron (i.e. Haze) • Ingredients for DM contribution: • Calculate e+/- injection spectrum for WIMPs (i.e. per annihilation) • Calculate steady-statee+/- distribution in the galactic halo • Calculate fractional power of sync. rad. that e+/- of a given E contributes to a given frequency (e.g. K-band, 23GHz) • Calculate total flux radiated by e+/- along a given line of sight CWRU, February 2009

  20. Neutralino Models • Neutralino DM (LSP): • 4 Benchmark models: (Mixed) (Gaugino) (Gaugino) (Higgsino) CWRU, February 2009

  21. Steady-State e+/-distribution • Solve diffusion-loss equation: • Charged particles undergo random walk • Cylindrical (uniform) diffusion zone of depth 2L • Assume no re-acceleration of solar modulation CWRU, February 2009

  22. Steady-State e+/-distribution CWRU, February 2009

  23. Steady-State e+/-distribution CWRU, February 2009

  24. Synchrotron Radiation Spectrum • e+/-accelerated by galactic B-field, confined to helical paths • Lorentz factor =E/me • isotropic distribution of pitch angles  CWRU, February 2009

  25. Synchrotron Radiation Spectrum Only e+/-with 2>/B (i.e. x<1, E>12GeV) contribute significantly CWRU, February 2009

  26. Synchrotron Radiation Spectrum CWRU, February 2009

  27. DM Synchrotron Flux • Integrate along l.o.s. with inclination  wrt GC Synchrotron Power for individual e+/- CWRU, February 2009

  28. Results for DM Synchrotron Flux  Significant Boost Factors (BF) required for Haze! CWRU, February 2009

  29. Summary • There is a statistically significant residual emission surrounding GC remaining after fitting Free-Free, Dust and Sync. foregrounds. • Largely consistent results between Gibbs and ILC CMB estimators. • Haze can be significantly reduced by allowing for a slight spatial dependence in Synchrotron emission within 50° of GC, with a similar spectral dependence as that further out. • The DM contribution to the Haze depends sensitively on its fractional power to synchrotron emission for e+/-with 2>/B . • DM requires significant boosting in Synchrotron power (BF~100-1000) in order to account for Haze. • BF~100 may be obtainable from Dark Matter Substructures. CWRU, February 2009

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