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Reionization science from the CMB after Planck

Michael Mortonson

University of Chicago

July 2, 2009

Reionization Science from the CMB After Planck

Michael MortonsonU Chicago/KICP

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Outline

July 2, 2009

Reionization report from June 2008 Fermilab CMBPol workshop:Zaldarriaga, Colombo, Komatsu, Lidz,

Mortonson, Oh, Pierpaoli, Verde, & ZahnarXiv:0811.3918

• Current reionization constraints and expected improvements from Planck and CMBPol (large-scale polarization)

optical depth physical parameters (reionization sources) model-independent information

• Separating reionization from other phenomena (e.g. inflation)


July 2, 2009 Michael MortonsonU Chicago/KICP

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The End of Reionization

Fan, Carilli, & Keating (2006)



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Reionization from Large-Scale E-modes

July 2, 2009

• Free electrons from reionization rescatter CMB photons• Local quadrupole generates polarization• Scattering at low redshifts projects onto large angular scales



5July 2, 2009

WMAP

Optical depth: = 0.09 ± 0.02

Mortonson & Hu (2008)

Allowed effects of reionization at 6<z<30



6July 2, 2009

Planck and CMBPol

Expect improved constraints on:

• optical depth (time of reionization)

• parameters of physical reionization models

• general reionization histories



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Optical Depth

WMAP = 0.017

Planck = 0.005

CMBPol = 0.0025

[Fermilab report]

WMAP

CMBPol



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Optical Depth

Does the optical depth come from high z or low z?

[Fermilab report]

WMAP

Planck

CMBPol



9July 2, 2009

Physical Models

Simple model – assume that DM halos of mass M > Mmin hostradiation sources that ionize regions of mass M:

[Fermilab report]

WMAP

Planck

CMBPol



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General Reionization Histories• Models of reionization may not capture all relevant physical processes

• How much information about the general evolution of the ionization fraction can we get from large-scale CMB polarization (regardless of what it tells us about particular models)?



11July 2, 2009

General Reionization Histories• Models of reionization may not capture all relevant physical processes

• How much information about the general evolution of the ionization fraction can we get from large-scale CMB polarization (regardless of what it tells us about particular models)?

CAMB/CosmoMC module for general reionization models:

http://background.uchicago.edu/camb_rpc



12July 2, 2009

General Reionization Histories



13July 2, 2009

General Reionization Histories



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Reducing Reionization Confusion

• Stronger constraints on reionization parameters will improve constraints on parameters degenerate with reionization

• Example: inflationary features in CMB temperature and

polarization

July 2, 2009



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Adams et al (2001), Covi et al. (2006)

July 2, 2009

Inflationary features and reionization



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Inflationary features and reionization

Mortonson, Dvorkin, Peiris, & Hu (2009)

July 2, 2009

Planck: 2-3 CMBPol: 5-6



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Summary

• Future polarization data will improve constraints on reionization parameters – several times more precise than WMAP.

• Can measure up to ~5 parameters describing the ionization history.

• Precise determination of physical parameters or reconstruction of the ionization history will likely require additional information.

• Potential confusion between effects of reionization and other large-scale polarization parameters can be greatly reduced.

July 2, 2009

Download - Reionization science from the CMB after Planck

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