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The Cosmic Microwave Background

The Cosmic Microwave Background. Lecture 2 Elena Pierpaoli. Lecture 2 – secondary anisotropies. Primary anisotropies: scattering, polarization and tensor modes Effect on parameters Secondary anisotropies : gravitational ISW Early Late Rees- Sciama lensing

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The Cosmic Microwave Background

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  1. The Cosmic Microwave Background Lecture 2 Elena Pierpaoli

  2. Lecture 2 – secondary anisotropies • Primary anisotropies: • scattering, polarization and tensor modes • Effect on parameters • Secondary anisotropies: gravitational • ISW • Early • Late • Rees-Sciama • lensing • Secondary anisotropies: (Re-scattering) • Reionization (uniform and patchy) • Sunyaev-Zeldovich effect (thermal & kinetic)

  3. The decomposition of the CMB spectrum Challinor 04

  4. Line of sight approach Visibility function g Conformal Newtonian Synchronous gauge Seljak & Zaldarriaga 06

  5. Polarization Due to parity symmetry of the density field, scalar perturbations Have U=0, and hence only produce E modes.

  6. Scattering and polarization If there is no U mode to start with, scattering does not generate it. No B mode is generated. Scattering sources polarization through the quadrupole.

  7. Tensor modes In linear perturbation theory, tensor and scalar perturbations evolve independently. Parity and rotation symmetry are no longer satisfied with gravity waves. B modes could be generated, along with T and E.

  8. The tensor modes expansion Scattering only produces E modes, B Are produced through coupling with E And free streaming.

  9. Power spectra for scalar and tensor perturbations Tensor to scalar ratio r=1

  10. Effect of parameters • Effect of various parameters on the T and P spectrum

  11. Fluctuation on scale  enters the horizon Derelativization Expan. factor a Matter dominated Radiation dominated Neutrinos free-stream heavy Neutrinos do not free-stream (I.e. behave like Cold Dark Matter) light Recombination (T=0.25 eV) 1)Neutrino mass: Physical effects on fluctuations on expansion • change the expansion rate • Change matter-radiation equivalence (but not recombination)

  12. Expan. factor a Matter dominated Radiation dominated Recombination 2) The relativistic energy density Nn Nn = (rrad - rg) / r1n 3 >3 • Effects: • change the expansion rate • Change matter-radiation equivalence (but not the radiation temperature, I.e. not recombination) • Model for: • neutrino asymmetry • other relativistic particles • Gravitational wave contribution

  13. Neutrino species Bell, Pierpaoli, Sigurdson 06

  14. Neutrino interactions Bell Pierpaoli Sigurdson 06

  15. Late ISW

  16. ISW-Galaxy cross correlation Giannantonio 08

  17. Rees Sciama effect Seljak 1996

  18. Lensing: temperature Lewis & Challinor 2006

  19. Lensing: polarization

  20. Lensing: B polrization

  21. Reionization: overall suppression

  22. t = 0.0845 Reionization: large scale effects

  23. Reionization

  24. 4) Neutrinos & reionization • Motivation: High redshift reionization required by the TP WMAP CMB power spectrum (t= 0.17), but difficult for stars to reionize “so early”.Decaying particles may provide partial reionization at high redshift. The neutrino decay model Hansen & Heiman 03 np + e e + g e + g Inverse Compton H + g H+ + e- Photoionization H + e-H+ +e- + e- Collisional ionization

  25. Standard parameters x Neutrino model parameters Reionization history Pierpaoli2004 • mass mn = 140-500 MeV , • Ee = 0 -180 MeV. • time decay: t15 = t/ 1015s = 2-10 • abundance: Wn = 10-9 Ionization fraction X= nH,ion / nH,total

  26. Standard parameters x Power spectra • High reionization from decay particles produce a too high optical depth and a too weird TP spectrum • High-z reionization from stars still needed • Long decay times and low abundances are preferred Pierpaoli2004

  27. Annihilating matter and reionization Mapelli Ferrara Pierpaoli 06 Slatyer et al 09

  28. Ostriker-Vishniac effect & patchy reionization Zhang et al 04 Santos et al 03 OV present even if reionization is uniform

  29. cluster g g e- Cluster number counts Cosmology with future surveys: Cluster power spectrum TheSunyaev-Zeldovichthermal signature Frequencies of observation DT/T = f(n) y y  Te ne • -Typical dimension: 1-10 arcmin • - Typical intensity: 10-4 K • - Signal is independent of cluster ‘sredshift • - Signal scales as ne • - Need complementary information on redshift from other data. • Both high resolution (SPT, ACT..) • And low resolution/all-sky (Planck) planned

  30. Clusters number counts Aghanim et al 08 Cluster counts depend mainly on sigma_8, Omega_m, w, and the flux threshold of the survey

  31. SZ thermal effect-Power spectrum

  32. SZ kinetic effect -Same frequency dependence as CMB (difficult to separate) -typically subdominant to Th SZ (5% of the ThSZ signal)

  33. SZ polarization produced by • Primordial quadrupole (reducing cosmic variance, probing large scale power) • cluster’s transverse velocity • Clusters’ magnetic fields • Double scattering within the cluster

  34. Magnitude of SZ polarization Liu et al 2005

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