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arXiv 0811.4280astro-ph
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五年威尔金森微波各向异性探测器(WMAP)观测:CMB极化图的贝叶斯估计

Five-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Bayesian Estimation of CMB Polarization Maps

J. Dunkley, D. N. Spergel, E. Komatsu, G. Hinshaw, D. Larson, M. R. Nolta, N. Odegard, L. Page, C. L. Bennett, B. Gold, R. S. Hill, N. Jarosik, J. L. Weiland, M… 展开作者

J. Dunkley, D. N. Spergel, E. Komatsu, G. Hinshaw, D. Larson, M. R. Nolta, N. Odegard, L. Page, C. L. Bennett, B. Gold, R. S. Hill, N. Jarosik, J. L. Weiland, M. Halpern, A. Kogut, M. Limon, S. S. Meyer, G. S. Tucker, E. Wollack, E. L. Wright

摘要:

我们描述了一种采样方法来估计偏振CMB信号从观测到的天空地图。我们使用Metropolis-within-Gibbs算法来估计极化CMB图,其中包含每个像素处的Q和U Stokes参数及其协方差矩阵。这些可以作为宇宙学分析的输入。偏振天空信号被参数化为三个分量的总和:CMB,同步辐射,和热尘埃排放。偏振银河系组件建模与空间变化的幂律光谱指数的同步加速器,和一个固定的幂律的灰尘,和他们的组件地图估计为副产品。我们将该方法应用于模拟低分辨率地图与像素的边7.2度,使用对角和全噪声实现绘制的WMAP噪声矩阵。CMB图以与误差一致的拟合优度恢复。对于固定的温度各向异性功率,计算图中E模式功率作为再电离光学深度τ的函数的可能性,对于输入τ =0.1的模拟,我们恢复τ =0.091+-0.019,并且平均τ =0.098,平均超过10次模拟。没有极化CMB信号的“零”模拟具有与τ =0一致的极大似然。该方法适用于五年的WMAP数据,使用K,Ka,Q和V通道。我们发现tau=0.090+-0.019,相比之下,在主要WMAP分析中使用的模板清洁图的tau=0.086+-0.016。同步加速器光谱指数β,在标准偏差σ(β)<0.25的高信噪比像素上平均,但不包括银河平面中被遮蔽的约6%的天空,为-3.03+-0.04。这个估计并不随银河系的纬度而显著变化,尽管包括了一个信息先验。

英文摘要:

We describe a sampling method to estimate the polarized CMB signal from observed maps of the sky. We use a Metropolis-within-Gibbs algorithm to estimate the polarized CMB map, containing Q and U Stokes parameters at each pixel, and its covariance matrix. These can be used as inputs for cosmological analyses. The polarized sky signal is parameterized as the sum of three components: CMB, synchrotron emission, and thermal dust emission. The polarized Galactic components are modeled with spatially varying power law spectral indices for the synchrotron, and a fixed power law for the dust, and their component maps are estimated as by-products. We apply the method to simulated low resolution maps with pixels of side 7.2 degrees, using diagonal and full noise realizations drawn from the WMAP noise matrices. The CMB maps are recovered with goodness of fit consistent with errors. Computing the likelihood of the E-mode power in the maps as a function of optical depth to reionization, tau, for fixed temperature anisotropy power, we recover tau=0.091+-0.019 for a simulation with input tau=0.1, and mean tau=0.098 averaged over 10 simulations. A `null' simulation with no polarized CMB signal has maximum likelihood consistent with tau=0. The method is applied to the five-year WMAP data, using the K, Ka, Q and V channels. We find tau=0.090+-0.019, compared to tau=0.086+-0.016 from the template-cleaned maps used in the primary WMAP analysis. The synchrotron spectral index, beta, averaged over high signal-to-noise pixels with standard deviation sigma(beta)<0.25, but excluding ~6% of the sky masked in the Galactic plane, is -3.03+-0.04. This estimate does not vary significantly with Galactic latitude, although includes an informative prior.

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