Faraday Rotation as a Diagnostic of Galactic Foreground Contamination of CMB Maps

Abstract

We present a diagnostic test of possible Galactic contamination of cosmic microwave background sky maps designed to provide an independent check on the methods used to compile these maps. The method involves a non-parametric measurement of cross-correlation between the Faraday rotation measure (RM) of extragalactic sources and the measured microwave signal at the same angular position. We argue that statistical properties of the observed distribution of rotation measures are consistent with a Galactic origin, an argument reinforced by a direct measurement of cross-correlation between dust, free-free and synchrotron foreground maps and RM values with the strongest correlation being for dust and free-free. We do not find any statistically compelling evidence for correlations between the RM values and the COBE DMR maps at any frequency, so there is no evidence of residual contamination in these CMB maps. On the other hand, there is a statistically significant correlation of RM with the preliminary WMAP individual frequency maps which remains significant in the Tegmark et al. Wiener-filtered map but not in the Internal Linear Combination map produced by the WMAP team.

arXiv comment8 pages, 1 figure, accepted for publication in MNRAS

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• Testing Gaussian random hypothesis with the cosmic microwave background temperature anisotropies in the three-year WMAP data
• Statistics of phase correlations as a test for non-Gaussianity of the CMB maps
• A Faraday Rotation Template for the Galactic Sky
• Non-Random Phases in Non-Trivial Topologies
• Random-Walk Statistics and the Spherical Harmonic Representation of CMB Maps
• Faraday Rotation as a diagnostic of Galactic foreground contamination of CMB maps
• Auto and cross correlation of phases of the whole-sky CMB and foreground maps from the 1-year WMAP data
• The One-dimensional Fourier Representation and Large Angular Scale Foreground Contamination in the 3-year Wilkinson Microwave Anisotropy Probe data
• Spectral analysis in orbital/superorbital phase space and hints of superorbital variability in the hard X-rays of LS I +61 303
• Peculiarities of phases of the WMAP quadrupole
• Statistical properties of polarized CMB foreground maps
• Cross-correlation analysis of CMB with foregrounds for residuals
• The synchrotron foreground and CMB temperature-polarization cross correlation power spectrum from the first year WMAP data
• Phase statistics of the WMAP 7 year data
• Detectability of Galactic Faraday Rotation in Multi-wavelength CMB Observations: A Cross-Correlation Analysis of CMB and Radio Maps