Bayesian Analysis of an Anisotropic Universe Model: Systematics and Polarization

We revisit the anisotropic universe model previously developed by Ackerman, Carroll, and Wise (ACW), and both the theoretical and computational framework to include polarization and various forms of systematic . We apply our new tools to simulated Wilkinson Microwave Anisotropy Probe (WMAP) data in order to the potential impact of asymmetric beams, noise misestimation, and potential zodiacal light emission. find that neither has any significant impact on the results. We next show that the previously reported ACW is also present in the one-year WMAP temperature sky map presented by Liu & Li, where data cuts are more . Finally, we re-analyze the five-year WMAP data taking into account a previously neglected (−i)^(l−l')-term the signal covariance matrix. We still find a strong detection of a preferred direction in the temperature map. multipoles up to ℓ = 400, the anisotropy amplitude for the W band is found to be g = 0.29 ± 0.031, at 9σ. However, the corresponding preferred direction is also shifted very close to the ecliptic poles at (l, b) = (96, 30), in agreement with the analysis of Hanson & Lewis, indicating that the signal is aligned along the of the solar system. This strongly suggests that the signal is not of cosmological origin, but most likely is a of an unknown systematic effect. Determining the nature of the systematic effect is of vital importance, as might affect other cosmological conclusions from the WMAP experiment. Finally, we provide a forecast for the experiment including polarization.