Non-Gaussian distribution and clustering of hot and cold pixels in the five-year WMAP sky |
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| Authors: | Graziano Rossi Ravi K Sheth Changbom Park Carlos Hernández-Monteagudo |
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| Institution: | Korea Institute for Advanced Study, Hoegiro 87, Dongdaemun-Gu, Seoul 130-722, Korea;Department of Physics and Astronomy, University of Pennsylvania, 209 South 33rd Street, Philadelphia, PA 19104-6396, USA;Max-Planck-Institut fuer Astrophysik, Karl-Schwarzschild Str. 1, D-85741 Garching bei Muenchen, Germany |
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| Abstract: | We present measurements of the clustering of hot and cold patches in the microwave background sky as measured from the Wilkinson Microwave Anisotropy Probe 5-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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| Keywords: | methods: data analysis methods: statistical cosmic microwave background cosmology: observations early Universe Large-scale structure of Universe |
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