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

Explore the standard model of the universe through CMB observations, anisotropies, polarization measurements, and spectral distortions. Unravel the mysteries of the early universe and implications for dark matter and dark energy. How does the CMB unveil the thermal history and evolution of our cosmos?

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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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