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arXiv 0906.2190astro-ph.COastro-ph.GA
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WMAP五年天象中冷热象元的非高斯分布和聚簇

Non-Gaussian Distribution and Clustering of Hot and Cold Pixels in the WMAP Five-Year Sky

Graziano Rossi, Ravi K. Sheth, Changbom Park, Carlos Hernandez-Monteagudo

摘要:

我们目前的测量集群的热和冷补丁的微波背景天空测量威尔金森微波各向异性探测器(WMAP)的五年数据。这些测量结果与理论预测相比,假设宇宙学信号服从高斯统计。我们发现显着的差异,从最简单的基于高斯的预测。然而,测量对噪声在空间上不均匀(例如,因为天空的不同部分被观察了不同的时间长度)。我们将展示如何在进行预测时考虑这种空间不均匀性。即使在对噪声进行了更仔细的计算之后,与基于高斯的期望值的差异仍然存在。特别是,我们注意到,热和冷的像素集群不同的温度阈值在几度尺度内。虽然这些发现可能表明原始的非高斯,我们讨论这些差异的其他合理的解释。此外,我们发现一些偏离高斯在次度尺度,特别是在W波段,其起源可能与河外尘埃排放。

英文摘要:

We present measurements of the clustering of hot and cold patches in the microwave background sky as measured from the Wilkinson Microwave Anisotropy Probe (WMAP) five-year data. These measurements are compared with theoretical predictions which assume that the cosmological signal obeys Gaussian statistics. We find significant differences from the simplest Gaussian-based prediction. However, the measurements are sensitive to the fact that the noise is spatially inhomogeneous (e.g., because different parts of the sky were observed for different lengths of time). We show how to account for this spatial inhomogeneity when making predictions. Differences from the Gaussian-based expectation remain even after this more careful accounting of the noise. In particular, we note that hot and cold pixels cluster differently within the same temperature thresholds at few-degree scales. While these findings may indicate primordial non-Gaussianity, we discuss other plausible explanations for these discrepancies. In addition, we find some deviations from Gaussianity at sub-degree scales, especially in the W band, whose origin may be associated with extragalactic dust emission.

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