CMB Temperature Polarization Correlation and Primordial Gravitational Waves: WMAP5

N J Miller,B G Keating,A G Polnarev

doi:10.1155/2009/309024

Abstract

we continue our study of the CMB temperature polarization (TE) cross-correlation as a source of information about primordial gravitational waves (PGWs). In a previous paper, we considered two methods for detecting PGWs using the TE cross-correlation. The first method is the zero multipole method, where we find the multipole,ℓ0, where the TE cross-correlation power spectrum,CℓTE, first changes sign. The second method Wiener filters the CMB TE data to remove the density perturbation contribution to the TE power spectrum. We then use statistical tests to determine if there is a detection of negative residual TE correlation and hence a detection of primordial gravitational waves, the only source of negative TE correlation at these superhorizon scales. In this paper, we will apply these tests to the WMAP 5-year data. We find that the TE power spectrum consistent withr< 2.0 at 95% confidence with no additional assumptions about the PGWs. If we assume that the PGWs are generated by inflation, then we getr< 1.0 at 95% confidence.

Highlights

The cosmic microwave background (CMB) has provided a wealth of information about cosmological phenomena
For the Wilcoxon rank sum test, the distribution of U is centered somewhat below the mean value we would get if r = 0 in the WMAP5 data
The S/N values are less than half of a standard deviation away from a value of zero, which they would be if the temperature polarization (TE) power spectrum due to density perturbations matched perfectly to the measured TE power spectrum

Summary

Introduction

The cosmic microwave background (CMB) has provided a wealth of information about cosmological phenomena. PGWs (tensor perturbations) generate negative temperature-polarization (TE) correlation for low multipoles, while primordial density (scalar) perturbations generate positive TE correlation for low multipoles (see [2, 4,5,6]). This signature can be used to detect or constrain the amount of PGWs. The tests formulated from this signature are useful as an insurance against false detection of PGWs using the BB power spectrum or as a way to monitor imperfectly subtracted systematic effects and foregrounds.

TE Cross-Correlation and Detection of PGWs

Discussion and Results

Conclusion