A note on the large-angle anisotropies in the WMAP cut-sky maps

TL;DR

This paper investigates large-angle anisotropies in WMAP data, confirming a significant preferred axis in the CMB that persists even after masking contaminated regions, indicating robustness of this anisotropy feature.

Contribution

The authors introduce a directional indicator for analyzing large-scale CMB anisotropies and demonstrate its effectiveness in identifying a robust preferred axis in WMAP data.

Findings

A statistically significant preferred direction in the CMB maps.

The main anisotropy feature remains after masking high-contamination regions.

Other subtle anomalies are no longer present after masking.

Abstract

Recent analyses of the WMAP data seem to indicate the possible presence of large-angle anisotropy in the Universe. If confirmed, these can have important consequences for our understanding of the Universe. A number of attempts have recently been made to establish the reality and nature of such anisotropies in the CMB data. Among these is a directional indicator recently proposed by the authors. A distinctive feature of this indicator is that it can be used to generate a sky map of the large-scale anisotropies of the CMB maps. Applying this indicator to full-sky temperature maps we found a statistically significant preferred direction. The full-sky maps used in these analyses are known to have residual foreground contamination as well as complicated noise properties. Thus, here we performed the same analysis for a map where regions with high foreground contamination were removed. We find that the main feature of the full-sky analysis, namely the presence of a significant axis of asymmetry, is robust with respect to this masking procedure. Other subtler anomalies of the full-sky are on the other hand no longer present.