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Reionization and the CMB

Reionization and the CMB. Joanna Dunkley University of Oxford. Ringberg, March 26 2009. The ‘early’ CMB signal. Linear theory Basic elements have been understood for 30 years (Peebles, Sunyaev & Zeldovich).

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Reionization and the CMB

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  1. Reionization and the CMB • Joanna Dunkley • University of Oxford Ringberg, March 26 2009

  2. The ‘early’ CMB signal Linear theory Basic elements have been understood for 30 years (Peebles, Sunyaev & Zeldovich)

  3. Electron effect 1: reionization damps the temperature fluctuations for l>40. Almost degenerate with overall amplitude. Nolta et al 2009

  4. Electron effect 2: CMB polarization Generated at recombination by viscosity of photon-baryon fluid (E-modes) Generated at reionization by scattering of CMB quadrupole off electrons t z=1000 z~7

  5. WMAP5 polarization Hinshaw et al 2009

  6. WMAP observations TE EE BB upper limit (Nolta et al 2009) Page et al 2007

  7. Constraints on tau and z (Dunkley et al 2009) Optical Depth to reionization: • Tau(5yr) = 0.087 +/- 0.017 (Dunkley et al 2009) • Tau(3yr) = 0.089 +/- 0.030 (Spergel et al 2007) Measure z=11.0 +-1.4 for sudden reionization

  8. Reionization histories Two-step model, ending at z=7 (Dunkley et al 2009) (Mortonson & Hu 2008)

  9. Prospects for Planck (Planck Blue Book) (Mortonson & Hu 2008)

  10. Modifications: including helium • ‘Old’ history (blue dashed) • ‘New’ history (black/red) • Leads to ~5% reduction in reionization redshift from CMB measurements (delta z~0.5) • ‘Standard’ history has some width, what to use? (Lewis 2008)

  11. Small-scale signatures MovingElectrons • Velocity of hot electrons from ionization by stars. Emit isotropically in electron rest frame. • Linear OV: linear fluctuations in density and velocity from time of reionization (reionization effect 3) • Non-linear kSZ: non-linear fluctuations from e.g. cluster velocities • Patchy kSZ: fluctuations in delta_x during reionization (reionization effect 4)

  12. Predicted power spectra (From Zahn et al 2005, in Zaldarriaga et al 2008 CMBPol report) (Iliev, Mellema, Pen, Bond, Shapiro 2008)

  13. Prospects with ACT/SPT 1.4°x 1.4° CMB (Iliev et al 2008) • Will be hard to distinguish patchy signal from OV/kSZ • Remove non-linear kSZ by identifying clusters • If extract signal, tell us about epoch and scales of bubbles • Could skew cosmological results if ignore KSZ/OV

  14. Summary • Reionization shows up in CMB in a few ways • Damping of fluctuations at all scales l>40 • Large-scale polarization signal • Small-scale OV signal • Small-scale patchy reionization signal • With WMAP we have detected large-scale pol signal, will be able to tell more about optical depth and history from Planck • With ACT and SPT we can attempt to find OV signal and patchy reionization signal, that will tell us more about reionization epoch.

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