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arXiv 0801.0554astro-ph
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CMB温度谱和偏振功率谱的似然分析

Likelihood Analysis of CMB Temperature and Polarization Power Spectra

Samira Hamimeche, Antony Lewis

摘要:

微波背景温度和偏振观测是一个强有力的方式来约束宇宙学参数,如果可以精确计算的似然函数。温度场和偏振场是相关的,部分天空覆盖相关的功率谱估计在不同的ell,和似然函数的理论频谱给定一组观测估计是非高斯的。准确的分析必须对所有这些属性进行建模。大多数现有的似然近似对于仅温度的分析是足够好的,但是它们不能可靠地处理温度-偏振相关性。我们给出了一个新的一般近似适用于相关的高斯场观测的天空的一部分。近似模型的非高斯形式,正是在理想的全天空限制,是快速评估使用预先计算的协方差矩阵和功率谱估计。我们的模拟表明,它是足够好的,以获得正确的结果在ell >~ 30的精确计算变得不可能。我们还表明,一些高斯近似提供可靠的参数约束,即使他们不捕捉的形状的似然函数在每个单元准确。最后,我们测试的模拟与现实各向异性噪声和不对称的前景掩模的近似。

英文摘要:

Microwave background temperature and polarization observations are a powerful way to constrain cosmological parameters if the likelihood function can be calculated accurately. The temperature and polarization fields are correlated, partial sky coverage correlates power spectrum estimators at different ell, and the likelihood function for a theory spectrum given a set of observed estimators is non-Gaussian. An accurate analysis must model all these properties. Most existing likelihood approximations are good enough for a temperature-only analysis, however they cannot reliably handle a temperature-polarization correlations. We give a new general approximation applicable for correlated Gaussian fields observed on part of the sky. The approximation models the non-Gaussian form exactly in the ideal full-sky limit and is fast to evaluate using a pre-computed covariance matrix and set of power spectrum estimators. We show with simulations that it is good enough to obtain correct results at ell >~ 30 where an exact calculation becomes impossible. We also show that some Gaussian approximations give reliable parameter constraints even though they do not capture the shape of the likelihood function at each ell accurately. Finally we test the approximations on simulations with realistically anisotropic noise and asymmetric foreground mask.

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