The Cosmic Microwave Background: Galactic Foregrounds and Faraday Rotation

This paper analyzes the cosmic microwave background (CMB) to determine the amount of influence each source of foreground contamination has on the microwave background measurements in relation to Faraday rotation. This study extends the analysis of Dineen and Coles, where the authors performed a novel analysis of the correlation between the Faraday rotation measure (RM), Wilkinson Microwave Anisotropy Probe (WMAP) sky maps, and CMB maps. Their technique has been replicated for numerous experiments analyzing the CMB. At the time, Dineen and Coles could only use a small Faraday RM dataset to test their hypothesis. With the advent of large, modern, and accurate Faraday rotation data, Dineen and Coles’ hypothesis can be validated on a larger scale. We hypothesize that contaminated foreground maps will have more significant and complete cross-correlation with RM than determined by Dineen and Coles. Over 41,000 sources of new RM data were used, compared to the approximately 600 RM sources Dineen and Coles used, allowing for a more definite conclusion about the potential for contamination analysis in temperature maps. Ultimately, a strong correlation was found between the RM and unprocessed CMB maps, but not between RM and the foreground- removed CMB maps, demonstrating the value of cross- correlation between Faraday RM and CMB as a diagnostic for foreground contamination. These results support the conclusions drawn by Dineen and Coles.