Model-independent reionization observables in the CMB

Hu, Wayne; Holder, G. P.

doi:10.1103/physrevd.68.023001

Cited by 110 publications

(137 citation statements)

References 11 publications

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“…We also checked that Planck data do not allow for model-independent reconstruction of x e in redshift bins. Principal component analysis has been proposed as an explicit approach to try to capture the details of the reionization history in a small set of parameters (Hu & Holder 2003;Mortonson & Hu 2008). Although these methods are generally considered to be non-parametric, they are in fact based on a description of x e (z) .…”

Section: Parametrization Of Reionization Historymentioning

confidence: 99%

Planckintermediate results

Adam

Aghanim

Ashdown

et al. 2016

A&A

406

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We investigate constraints on cosmic reionization extracted from the Planck cosmic microwave background (CMB) data. We combine the Planck CMB anisotropy data in temperature with the low-multipole polarization data to fit ΛCDM models with various parameterizations of the reionization history. We obtain a Thomson optical depth τ = 0.058±0.012 for the commonly adopted instantaneous reionization model. This confirms, with data solely from CMB anisotropies, the low value suggested by combining Planck 2015 results with other data sets, and also reduces the uncertainties. We reconstruct the history of the ionization fraction using either a symmetric or an asymmetric model for the transition between the neutral and ionized phases. To determine better constraints on the duration of the reionization process, we also make use of measurements of the amplitude of the kinetic Sunyaev-Zeldovich (kSZ) effect using additional information from the high-resolution Atacama Cosmology Telescope and South Pole Telescope experiments. The average redshift at which reionization occurs is found to lie between z = 7.8 and 8.8, depending on the model of reionization adopted. Using kSZ constraints and a redshift-symmetric reionization model, we find an upper limit to the width of the reionization period of ∆z < 2.8. In all cases, we find that the Universe is ionized at less than the 10% level at redshifts above z 10. This suggests that an early onset of reionization is strongly disfavoured by the Planck data. We show that this result also reduces the tension between CMB-based analyses and constraints from other astrophysical sources.

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Section: Parametrization Of Reionization Historymentioning

confidence: 99%

Planckintermediate results

Adam

Aghanim

Ashdown

et al. 2016

A&A

406

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“…However, the degeneracy between the binned ionization fraction leads to weak constraints [20]. The principal component analysis provides a solution to this problem [7].…”

Section: Modelmentioning

confidence: 99%

“…1, we can cut off ℓ safely to ℓ max = 100 in the Fisher matrix. The perturbation to the fiducial x fid e is a delta function correlated with the nearby region [7]. The Fisher matrix F ij is decomposed as…”

Section: Modelmentioning

confidence: 99%

“…The position of the bump is proportional to the square root of the redshift at which the reionization occurs, while the amplitude is proportional to the optical depth [4,5]. Therefore, measurements of the large-scale polarization angular power spectra can be used to constrain the reionization history [6,7]. Current constraint on the reionization optical depth from the Planck temperature data in combination with the low-multipole polarization data is τ = 0.078 ± 0.019 in the base ΛCDM model [8], which is smaller than τ = 0.089 ± 0.014 estimated by the WMAP 9-year data [9], but consistent with that from WMAP polarization measurements cleaned for dust emission using 353 GHz polarization maps from the high frequency instrument [10].…”

Section: Introductionmentioning

confidence: 99%

“…Hu and Holder proposed a principal component analysis (PCA) of the reionization history to quantity the information contained in the large-scale E-mode polarization [7]. The principal components are the eigenfunctions of the Fisher matrix that describes the dependence of the polarization angular power spectra on the reionization history.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Principal component analysis of the reionization history from Planck 2015 data

2015

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The simple assumption of an instantaneous reionization of the Universe may bias estimates of cosmological parameters. In this paper a model-independent principal component method for the reionization history is applied to give constraints on the cosmological parameters from recent Planck 2015 data. We find that the Universe are not completely reionized at redshifts z ≥ 8.5 at 95% CL. Both the reionization optical depth and the matter fluctuation amplitude are higher than but consistent with those obtained in the standard instantaneous reionization scheme. The high estimated value of the matter fluctuation amplitude strengthens the tension between Planck CMB observations and some astrophysical data, such as cluster counts and weak lensing. The tension can significantly be relieved if the neutrino masses are allowed to vary. Thanks to a high scalar spectral index, the low-scale spontaneously broken SUSY inflationary model can fit the data well, which is marginally disfavored at 95% CL in the Planck analysis.

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Cosmic Microwave Background Polarization Analysis

Challinor¹

2008

Data Analysis in Cosmology

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With polarization of the cosmic microwave background (CMB) now detected, and confirmed by several independent experiments, the next goal is to characterise accurately its statistical properties. In these lecture notes we review the physical motivation for pursuing CMB polarization, and the basic statistical properties of the polarization fields. We then discuss some of the key aspects of the analysis of CMB polarization data, focusing on the additional complications that arise compared to temperature data due to the tensor character of the polarization field.

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Model-independent reionization observables in the CMB

Cited by 110 publications

References 11 publications

Planckintermediate results

Planckintermediate results

Principal component analysis of the reionization history from Planck 2015 data

Cosmic Microwave Background Polarization Analysis

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