reionization and the cmb
DESCRIPTION
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). - PowerPoint PPT PresentationTRANSCRIPT
Reionization and the CMB
Joanna DunkleyUniversity of Oxford
Ringberg, March 26 2009
The ‘early’ CMB signal
Linear theoryBasic elements have been
understood for 30 years (Peebles, Sunyaev & Zeldovich)
Nolta et al 2009
Electron effect 1: reionization damps the temperature fluctuations for l>40.
Almost degenerate with overall amplitude.
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
z=1000
z~7t
WMAP5 polarization
Hinshaw et al 2009
TE
EE
BB upper limit
Page et al 2007
WMAP observations
(Nolta et al 2009)
Constraints on tau and z
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
(Dunkley et al 2009)
Reionization histories
Two-step model, ending at z=7 (Dunkley et al 2009)
(Mortonson & Hu 2008)
Prospects for Planck
€
σ(τ )WMAP 5 = 0.017
σ (τ )Planck = 0.005
σ (τ )CV = 0.002
(Planck Blue Book)
(Mortonson & Hu 2008)
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)
Small-scale signatures
Velocity of hot electrons from ionization by stars. Emit isotropically in electron rest frame.
1.Linear OV: linear fluctuations in density and velocity from time of reionization (reionization effect 3)2.Non-linear kSZ: non-linear fluctuations from e.g. cluster velocities3.Patchy kSZ: fluctuations in delta_x during reionization (reionization effect 4)
Moving Electrons
Predicted power spectra
(From Zahn et al 2005, in Zaldarriaga et al 2008
CMBPol report)(Iliev, Mellema, Pen, Bond, Shapiro 2008)
CMB
KSZ/OV
Prospects with ACT/SPT1.4°x 1.4°
• 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
(Iliev et al 2008)
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.