Probing non-Gaussianities on Large Scales in WMAP5 and WMAP7 Data using Surrogates

TL;DR

This study investigates large-scale non-Gaussianities in WMAP CMB data using surrogate data methods, revealing significant signatures that challenge standard cosmological models and assumptions of isotropy.

Contribution

It introduces a model-independent surrogate data approach to detect non-Gaussianities and asymmetries in the CMB on large scales, providing new evidence against the standard inflationary paradigm.

Findings

Significant non-Gaussianities detected on large scales in WMAP data.

Results consistent across different WMAP data releases.

Findings challenge the principle of isotropy and standard inflation models.

Abstract

Probing Gaussianity represents one of the key questions in modern cosmology, because it allows to discriminate between different models of inflation. We test for large-scale non-Gaussianities in the cosmic microwave background (CMB) in a model-independent way. To this end, so-called first and second order surrogates are generated by first shuffling the Fourier phases belonging to the scales not of interest and then shuffling the remaining phases for the length scales under study. Using scaling indices as test statistics we find highly significant signatures for both non-Gaussianities and asymmetries on large scales for the WMAP data of the CMB. We find remarkably similar results when analyzing different ILC-maps based on the WMAP five and seven year data. Such features being independent from the map-making procedure would disfavor the fundamental principle of isotropy as well as canonical single-field slow-roll inflation - unless there is some undiscovered systematic error in the collection or reduction of the CMB data or yet unknown foreground contributions.