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Proprieta’ fini della Radiazione Fossile una sonda verso l’ Universo primordiale

Proprieta’ fini della Radiazione Fossile una sonda verso l’ Universo primordiale. Giorgio Sironi Dipartimento di Fisica G. Occhialini Universita` degli Studi di Milano Bicocca. Time – Distance relation / = v/c = Ho d. (H0 = 75 km/sec Mpc = 1/(15 10 9 anni)).

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Proprieta’ fini della Radiazione Fossile una sonda verso l’ Universo primordiale

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  1. Proprieta’ fini della Radiazione Fossileuna sonda verso l’ Universo primordiale Giorgio Sironi Dipartimento di Fisica G. Occhialini Universita` degli Studi di Milano Bicocca INRIM-Torino

  2. Time – Distance relation/ = v/c = Ho d (H0 = 75 km/sec Mpc = 1/(15 109 anni)) INRIM-Torino

  3. Cosmic Microwave Background Discovery Penzias and Wilson 1964 INRIM-Torino

  4. CMB and the Standard Model of the Universe A short thermal history ( N.B. Scale Factor R = 1/(1+Z) ) INRIM-Torino

  5. Standard Model CMB First Order properties • No polarization • Isotropic distribution • Planckian spectrum • TCMB(Z) = TCMB(0)(1+Z) ? INRIM-Torino

  6. Standard ModelCMB Second order effects - Spectral distortions - Spatial Anisotropies - Residual Polarization - S.Z. effect INRIM-Torino

  7. CMB Anisotropies : observation COBE ~1990 WMAP ~2000 INRIM-Torino

  8. CMB Anisotropies : results Power spectrum Power versus angular scale (multipole order) INRIM-Torino

  9. CMB Anisotropies Astrophysical implications Geometry of the Universe flat Universe dominated by Dark Matter and Dark Energy INRIM-Torino

  10. CMB Polarization measurements WMAP results correlation with anisotropy Polarized signal K INRIM-Torino

  11. CMB Polarization measurements astrophisical implications • Precise estimate of H0 • → Big Bang 13.7 10^9 years • ago • regular expansion since the • Big Bang • very rapid exponential • expansion during the first • 10-32 sec ("inflation“): highly • probable • Universe reionization • at Z~(20-100) INRIM-Torino

  12. Sunyaev – Zeldovich effect • CMB photons scattered by the intracluster medium in clusters of galaxies • - INRIM-Torino

  13. Sunyaev – Zeldovich effect The CMB temperature measured against a cluster is lower (higher) show a lowest (higher) at low (high) frequencies • observation used to get : • properties of intracluster medium • dependence of TCMB on Z • absolute measurements of Hubble constant INRIM-Torino

  14. CMB and Standard Model Second order effects • Spatial Anisotropies  • Residual Polarization () • S.Z effect  • Spectral distortions ? • Spectral distortions: • a tool to investigate the thermal history of the • Universe • - allow to push observational cosmology beyond the • last scattering surface. INRIM-Torino

  15. The CMB frequency spectrum Expected spectral distortions INRIM-Torino

  16. The CMB spectrum origin of distortions Energy Injections (turbulence dissipation, particle annihilation, etc. … Matter - radiation interactions + + Universe expansion  Kompaneets Equation (Kompaneets 1957, Danese and De Zotti 1977, 1978,1980 Burigana et al. 1991, Daly 1991) INRIM-Torino

  17. The CMB spectrum distortions Distortions depends on : i)energy injections Δε/ε ii)epoch of injections Z iii)barion density Ωb Three scenarios INRIM-Torino

  18. The CMB spectrum expected distortions Z >107 thermal equilibrium (Planck distribution) reestablished immediately. No distortion expected 107 > Z > 104 semi-equilibrium spectrum established (BoseEistein distribution). Distortions do not depend on the energy injection process Z < 104 no equilibrium spectrum. Distortion shape andfrequency depend on the generation process INRIM-Torino

  19. The CMB spectrum sources of expected distortions Possible Energy Injection Mechanisms • Dissipation of adiabatic fluctuations in the photon- baryon fluid • (Barrow&Coles, MNRAS,1991) but for sudden (Dirac delta) injection • Dissipation of turbulent motions (Ozernoi&Chernin, Sov.Phys., 1968) • Decay of massive particles and Matter-Antimatter annihilation • other possible sources of energy injection • (e.g. Partridge, 1995 and references therein ) • ……………… INRIM-Torino

  20. The evolution of the spectrum before recombination (II) INRIM-Torino

  21. The evolution of the spectrum before recombination (II) Full thermodynamical equilibrium (Planck spectrum) Kinetic equilibrium (Bose-Einstein spectrum) The solution of the kinetic equation is a superposition of blackbody spectra at different temperatures INRIM-Torino

  22. The evolution of the spectrum before recombination (III) energy injections cannot be thermalized over all the frequency spectrum: spectrum comptonized Bremsstrahlung and DC effective at low frequencies BE spectrum with frequency-dependent chemical potential in presence of strong heating the distorted spectrum is xCB: frequency where Compton and Bremsstrahlung rate are comparable (BE distortion cancelled at low frequencies) References: Zeldovich&Sunyaev, Ap&SS 1969 Sunyaev&Zeldovich, Ap&SS, 1970 INRIM-Torino

  23. The CMB spectrum expected distortions Brightness Temperature for a given photon occupation number n(x) Bose-Einstein distortion Comptonization RJ W INRIM-Torino

  24. The CMB distorted spectrum expectations at low frequencies Extracting the Baryon density from Burigana, De Zotti & Danese, ApJ 379, 1991 INRIM-Torino

  25. The CMB spectral distortions Observations INRIM-Torino

  26. The CMB spectrum measurements The CMB spectrum measured by FIRAS/COBE (Mather et al. 1994) Tcmb = (2.725 +/- 0.001) K (Fixsen and Mather 2002) INRIM-Torino

  27. The CMB spectrum INRIM-Torino

  28. The CMB spectrum measurements INRIM-Torino

  29. The CMB spectrum energy injections: upper limits Under all circumstances (early or late injections) Δ/< 10-5 yB < 10-5 Mind - possibile different calibrations for FIRAS (Battistelli et al. 2000, N.Ast. 5, 77) - below 5 GHz large uncertainties For a complete analysis see for instance Salvaterra and Burigana (2003) MNRAS 342, 543 Nordberg and Smoot astro-ph/9805123 INRIM-Torino

  30. The CMB spectrum So far observation gave: • No evidence of deviations from a Planck frequency distribution (distortions) • Only upper limits For new observation an interesting region is the RJ low frequency region ( ~ 1 GHz) INRIM-Torino

  31. The CMB spectral distortions • Why • search based on comparison of absolute • measurements at different frequencies • systematic effects dominant INRIM-Torino

  32. Measurements of the CMB spectruman example of low frequency observation TRIS Absolute measurement of Tsky at 0.6, 0.82 and 2.5 GHz INRIM-Torino

  33. Extracting the CMB absolute temperature • TCMB()= Tsky(,,) – Tgal(,,) –Textrag() • Tsky =Tant- Tgro - Tatm • Tant =[Tref+ DT - Tamb(1 - e-t ) ]/ e-t • TambTref~TLHe~ TCMB •  never negligible, measurement difficult • Modelling necessary to disentangle the signals INRIM-Torino

  34. Extracting the CMB absolute temperature Last but not least Radio Interferences INRIM-Torino

  35. TRIS : measured profiles of the sky temperature at 600 and 820 MHz TRIS dec=+42 INRIM-Torino

  36. CMB search for spectral distortions at low frequencies Typical uncertainties of today measurements close to 1 GHz  0.6 GHz 0.82 GHz 2.5 GHz Tsky 0.2  0.1  0.05 Tatm  0.02  0.02  0.03 Tgro  0.05  0.05  0.05 Textr  0.015  0.07  0.03 Tgal  0.80  0.40 0.02  Today at  < 1 GHz TCMB/TCMB~ 30 % Insufficient to detect spectral distortions INRIM-Torino

  37. CMB Spectrum future observation ? • Necessary • Dedicated experiments in space (LOBO,DIME, … ) no approval so far With stratospheric balloons (>2 GHz) (ARCADE) From ground level INRIM-Torino

  38. CMB Spectrum future observation ? Possible way out Differential measurements of the sky temperature with standard radiotelescopes • using a celestial radio source with well known • spectrum as a reference level • at many frequencies • over a limited region of sky INRIM-Torino

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