Reionization history and CMB parameter estimation

TL;DR

This paper examines how uncertainties in the universe's reionization history impact cosmological parameter estimates from CMB data, finding simple models suffice for future data and PCA cannot accurately reconstruct reionization history.

Contribution

It demonstrates that simple reionization models do not bias parameter estimates and shows PCA's limitations in reconstructing realistic reionization histories.

Findings

Simple reionization models do not bias parameter estimates.

PCA cannot accurately reconstruct realistic reionization histories.

Reionization modeling complexity is unnecessary for future CMB data analysis.

Abstract

We study how uncertainty in the reionization history of the universe affects estimates of other cosmological parameters from the Cosmic Microwave Background. We analyze WMAP7 data and synthetic Planck-quality data generated using a realistic scenario for the reionization history of the universe obtained from high-resolution numerical simulation. We perform parameter estimation using a simple sudden reionization approximation, and using the Principal Component Analysis (PCA) technique proposed by Mortonson and Hu. We reach two main conclusions: (1) Adopting a simple sudden reionization model does not introduce measurable bias into values for other parameters, indicating that detailed modeling of reionization is not necessary for the purpose of parameter estimation from future CMB data sets such as Planck. (2) PCA analysis does not allow accurate reconstruction of the actual reionization history of the universe in a realistic case.