Monthly Notices of the Royal Astronomical Society · 2011 · 15 citations · 48 references
We present a model-independent investigation of the WMAP data with respect to\nscale- dependent non-Gaussianities (NGs) by employing the method of constrained\nrandomization. For generating so-called surrogate maps a shuffling scheme is\napplied to the Fourier phases of the original data, which allows to test for\nthe presence of higher order correlations (HOCs) on well-defined scales. Using\nscaling indices as test statistics we find highly significant signatures for\nnon-Gaussianities when considering all scales. We test for NGs in the bands l =\n[2,20], l = [20,60], l = [60,120] and l = [120,300]. We find highly significant\nsignatures for non-Gaussianities and ecliptic hemispherical asymmetries for l =\n[2, 20]. We also obtain highly significant deviations from Gaussianity for the\nband l = [120,300]. The result for the full l-range can be interpreted as a\nsuperposition of the signatures found in the bands l = [2, 20] and l = [120,\n300]. We find remarkably similar results when analyzing different ILC-like\nmaps. We perform a set of tests to investigate if the detected anomalies can be\nexplained by systematics. While no test can convincingly rule out the intrinsic\nnature of the anomalies for the low l case, the ILC map making procedure and/or\nresidual noise in the maps can also lead to NGs at small scales. Our\ninvestigations prove that there are phase correlations in the WMAP data of the\nCMB. In the absence of an explanation in terms of Galactic foregrounds or known\nsystematic artefacts, the signatures at low l must so far be taken to be\ncosmological at high significance. These findings strongly disagree with\npredictions of isotropic cosmologies with single field slow roll inflation. The\ntask is now to elucidate the origin of the phase correlations and to understand\nthe physical processes leading to these scale-dependent non-Gaussianities - if\nsystematics as cause for them must be ruled out.\n
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