各向异性宇宙模型的贝叶斯分析：系统学和极化
Bayesian analysis of an anisotropic universe model: systematics and polarization
摘要：
我们重新审视了阿克曼，卡罗尔和怀斯（ACW）以前开发的各向异性宇宙模型，并概括了理论和计算框架，包括极化和各种形式的系统效应。我们将我们的新工具应用于模拟的WMAP数据，以了解非对称光束，噪声错误估计和潜在的黄道光发射的潜在影响。我们发现，这两个都没有任何重大影响的结果。我们接下来表明，以前报道的ACW信号也存在于Liu & Li提出的1年WMAP温度天空图中，其中数据削减更为积极。最后，我们重新分析了5年的WMAP数据，考虑到以前忽略的（-i）^{l-l'}-长期的信号协方差矩阵。我们仍然在温度图中发现了对优选方向的强检测。包括多极高达l = 400，W波段的各向异性振幅被发现是g = 0.29 +-0.031，非零在9西格玛。然而，相应的优选方向也在（l，b）=（96，30）处非常接近黄道极点，与Hanson & Lewis的分析一致，表明信号沿着太阳系的平面排列。这强烈表明，信号不是宇宙学的起源，但最有可能是一个未知的系统效应的产物。确定系统效应的性质至关重要，因为它可能会影响WMAP实验的其他宇宙学结论。最后，我们提供了一个预测普朗克实验包括极化。
英文摘要：
We revisit the anisotropic universe model previously developed by Ackerman, Carroll and Wise (ACW), and generalize both the theoretical and computational framework to include polarization and various forms of systematic effects. We apply our new tools to simulated WMAP data in order to understand the potential impact of asymmetric beams, noise mis-estimation and potential Zodiacal light emission. We find that neither has any significant impact on the results. We next show that the previously reported ACW signal is also present in the 1-year WMAP temperature sky map presented by Liu & Li, where data cuts are more aggressive. Finally, we reanalyze the 5-year WMAP data taking into account a previously neglected (-i)^{l-l'}-term in the signal covariance matrix. We still find a strong detection of a preferred direction in the temperature map. Including multipoles up to l=400, the anisotropy amplitude for the W-band is found to be g = 0.29 +- 0.031, nonzero at 9 sigma. 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 plane of the solar system. This strongly suggests that the signal is not of cosmological origin, but most likely is a product of an unknown systematic effect. Determining the nature of the systematic effect is of vital importance, as it might affect other cosmological conclusions from the WMAP experiment. Finally, we provide a forecast for the Planck experiment including polarization.
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