Direct measurement of the angular power spectrum of cosmic microwave background temperature anisotropies in the WMAP Data

TL;DR

This paper presents a direct measurement of the CMB temperature anisotropy power spectrum using a novel flat sky Fourier analysis approach on WMAP data, avoiding traditional foreground cleaning issues.

Contribution

It introduces a method that directly estimates the angular power spectrum from WMAP data by analyzing small patches, bypassing the need for foreground cleaning and spherical harmonic orthogonality constraints.

Findings

Reproduces the first and second acoustic peaks.

Clearly detects the third peak with some noise residual.

Validates Gaussian statistical characteristics of the patches.

Abstract

Angular power spectrum of the cosmic microwave background (CMB) temperature anisotropies is one of the most important on characteristics of the Universe such as its geometry and total density. Using flat sky approximation and Fourier analysis, we estimate the angular power spectrum from an ensemble of least foreground-contaminated square patches from WMAP W and V frequency band map. This method circumvents the issue of foreground cleaning and that of breaking orthogonality in spherical harmonic analysis due to masking out the bright Galactic plane region, thereby rendering a direct measurement of the angular power spectrum. We test and confirm Gaussian statistical characteristic of the selected patches, from which the first and second acoustic peak of the power spectrum are reproduced, and the third peak is clearly visible albeit with some noise residual at the tail.