Non-Gaussianity of the distribution tails in CMB

TL;DR

This paper investigates the non-Gaussian features in the distribution tails of CMB temperature multipoles, identifying a sharp peak around l~45 that may indicate cosmic strings or gravitational waves rather than foreground contamination.

Contribution

It reveals a specific non-Gaussian tail behavior in CMB multipoles and suggests potential cosmological origins beyond galactic foregrounds.

Findings

Non-Gaussian tails peak sharply at l~45

Similar peaks across different frequency bands

Odd and even multipoles show opposite non-Gaussianities

Abstract

We analyze statistical properties of the separate multipole moments of the CMB temperature maps and find that the distribution tails are slightly non-Gaussian. Moreover, the deviation from Gaussianity peaks sharply at around $l\sim45\pm10$. If the detected non-Gaussianities should be attributed to the remaining foreground contamination from the galactic plane, an appearance of a similar peak in different frequency bands is unexpected. The presence of the peak was also confirmed by the analysis of weighted multipoles which is less susceptible to the galactic noise. A separate analysis of the multipoles with odd and even $l+m$ shows two opposite types of non-Gaussianities which cannot be explained with only galactic foregrounds. We argue that cosmic strings or correlated gravitational waves could lead to the observed effect.