Search for Non-Gaussianities in the WMAP Data with the Scaling Index Method

Figure 13

The probability densities 𝑃(𝛼) of the scaling indices for the first-(black) and second-order surrogates (coloured) of WMAP 7-year data, calculated for the largest scaling range 𝑟₁₀ and for the ℓ-interval Δℓ=[2,20]. Yellow (green) curves denote the densities for 20 realizations of second-order surrogates derived from the ILC7 (NILC5) map. The reference frame for defining the upper and lower hemispheres is chosen such that the difference Δ𝑆=𝑆_up−𝑆_low becomes maximal for ⟨𝛼⟩ of the respective map and respective scale 𝑟.

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