Cosmic Ray contribution to the WMAP polarization data on the Cosmic Microwave Background

TL;DR

This paper analyzes 9-year WMAP polarization data to investigate cosmic ray foreground contamination, especially at high Galactic latitudes, highlighting its impact on detecting primordial gravitational waves.

Contribution

It updates previous analyses by applying correlation methods to identify cosmic ray foregrounds in polarization data, emphasizing their persistence at high Galactic latitudes.

Findings

Cosmic ray foregrounds are present even at high Galactic latitudes.

Foreground contamination complicates the detection of inflationary gravitational waves.

Foreground effects need further study to accurately interpret CMB polarization.

Abstract

We have updated our analysis of the 9-year WMAP data using the collection of polarization maps looking for the presence of additional evidence for a finite 'cosmic ray foreground' for the CMB. We have given special attention to high Galactic latitudes, where the recent BICEP2 findings were reported. The method of examining the correlation with the observed gamma ray flux proposed in our earlier papers and applied to the polarization data shows that the foreground related to cosmic rays is still observed even at high Galactic altitudes and conclusions about gravitational waves are not yet secure. Theory has it that there is important information about inflationary gravitational waves in the fine structure of the CMB polarization properties (polarization vector and angle) and it is necessary to examine further the conclusions that can be gained from studies of the CMB maps, in view of the disturbing foreground effects.