Phase statistics of the WMAP 7 year data

Kovács, András and Szapudi, István and Frei, Zsolt (2013) Phase statistics of the WMAP 7 year data. ASTRONOMISCHE NACHRICHTEN, 334 (9). pp. 1020-1023. ISSN 0004-6337

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Abstract

We performed a comprehensive statistical analysis using complex phases of the alm coefficients computed from the most recent data of the Wilkinson Microwave Anisotropy Probe (WMAP). Our aim was to confirm or constrain the presence of non-Gaussianities in the data. We found phase correlations - that suggest non-Gaussianity - at high-l in alm coefficients by applying various statistical tests. Most of all, we detected a non-Gaussian signal reaching a significance of 4.7σ using random walk statistics and simulations. However, our conclusion is that the non-Gaussian behavior is due to contamination from galactic foregrounds that show up in small scales only. When masked out the contaminated regions, we found no significant non-Gaussianity. Furthermore, we constrained the fNL parameter using CMB simulations that mimic primordial non-Gaussianity. Our estimate is fNL = 40 ± 200, in agreement with previous measurements and inflationary expectations.

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