Mapping the large-angle deviation from Gaussianity in simulated CMB maps

Abstract

[Abridged] In recent works we have proposed two new large-angle non-Gaussianity indicators based on skewness and kurtosis of patches of CMB sky-sphere, and used them to find out significant deviation from Gaussianity in frequency bands and foreground-reduced CMB maps. Simulated CMB maps with assigned type and amplitude of primordial non-Gaussianity are important tools to determine the strength, sensitivity and limitations of non-Gaussian estimators. Here we investigate whether and to what extent our non-Gaussian indicators have sensitivity to detect non-Gaussianity of local type, particularly with amplitude within the seven-year WMAP bounds. We make a systematic study by employing our statistical tools to generate maps of skewness and kurtosis from several thousands of simulated maps equipped with non-Gaussianity of local type of various amplitudes. We show that our indicators can be used to detect large-angle local-type non-Gaussianity only for relatively large values of the non-linear parameter $f_{\mathrm{NL}}^{\mathrm{local}}$. Thus, our indicators have not enough sensitivity to detect deviation from Gaussianity with the non-linear parameter within the seven-year WMAP bounds. This result along with the outcomes of frequency bands and foreground-reduced analyses suggest that non-Gaussianity captured in the previous works by our indicators is not of primordial origin, although it might have a primordial component. We have also made a comparative study of non-Gaussianity of simulated maps and of the full-sky WMAP foreground-reduced seven-year ILC-7yr map. An outcome of this analysis is that the level of non-Gaussianity of ILC-7yr map is higher than that of the simulated maps for $f_{\mathrm{NL}}^{\mathrm{local}}$ within WMAP bounds. This provides quantitative indications on the suitability of the ILC-7yr map as a Gaussian reconstruction of the full-sky CMB.

9 pages, 5 figures, 3 tables. V2: Version published in PRD(2011). Appendix added. New figures, typos corrected, references added

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Cited by in corpus (13)

• Local analyses of Planck maps with Minkowski Functionals
• North-South non-Gaussian asymmetry in PLANCK CMB maps
• Searching for primordial non-Gaussianity in Planck CMB maps using a combined estimator
• Local properties of WMAP Cold Spot
• Tomographic local 2D analyses of the WISExSuperCOSMOS all-sky galaxy catalogue
• Excess of lensing amplitude in the Planck CMB power spectrum
• Moment analysis of highway-traffic clearance distribution
• Probing CMB Cold Spot through Local Minkowski Functionals
• A search for concentric rings with unusual variance in the 7-year WMAP temperature maps using a fast convolution approach
• Primordial Non-Gaussianities of inflationary step-like models
• Mapping possible non-Gaussianity in the Planck maps
• A comparative study of non-Gaussianity in ILC-7yr CMB map
• Searching for non-Gaussianity in the Planck data