Cosmological parameters from WMAP 5-year temperature maps

TL;DR

This paper presents an analysis of WMAP 5-year CMB temperature maps to estimate the power spectrum, evaluate fit quality, and constrain cosmological parameters, with slight improvements in error bars and discussions on reionization history.

Contribution

It introduces a hybrid cross-power spectrum estimator, assesses its fit, and explores reionization constraints, offering refined analysis methods for WMAP data.

Findings

Power spectrum error bars are slightly smaller than previous results.

Constraints on optical depth inform reionization history models.

Proposes new likelihood approximation for skewed chi-squared distributions.

Abstract

I calculate a hybrid cross-power spectrum estimator from the WMAP 5-year CMB temperature maps, discuss the goodness of fit, and then constrain cosmological parameters. The spectrum and results are generally consistent with previous results, though the power spectrum error bars are slightly smaller and there are small shifts at high ell. The small improvement in error bars is obtained at very low numerical cost but does not significantly improve parameter constraints. I discuss the accuracy of the likelihood model and how constraints on the optical depth translate into constraints on the reionization history allowing for helium reionization. In the appendices I propose a simple reionization parameterization that determines the history in terms of a mid-point reionization redshift, and suggest a new likelihood approximation for chi-squared-like distributions with varying skewness.