Large scale directional anomalies in the WMAP 5yr ILC map

TL;DR

This paper investigates large-scale directional anomalies in the WMAP 5-year ILC map, revealing statistically significant alignments of low multipoles with specific sky directions, suggesting potential anomalies in cosmic microwave background data.

Contribution

It provides a detailed statistical analysis of low multipole alignments in WMAP data, highlighting significant directional anomalies not explained by random chance.

Findings

Quadrupole and octupole are mildly orthogonal to the dipole.

Multipole vectors for ℓ=4 are unlikely aligned with the dipole.

Multipole vectors for ℓ=5 show significant orthogonality with the dipole.

Abstract

We study the alignments of the low multipoles of CMB anisotropies with specific directions in the sky (i.e. the dipole, the north Ecliptic pole, the north Galactic pole and the north Super Galactic pole). Performing $10^5$ random extractions we have found that: 1) separately quadrupole and octupole are mildly orthogonal to the dipole but when they are considered together, in analogy to \cite{Copi2006}, we find an unlikely orthogonality at the level of 0.8% C.L.; 2) the multipole vectors associated to $\ell=4$ are unlikely aligned with the dipole at $99.1 %$ C.L.; 3) the multipole vectors associated to $\ell=5$ are mildly orthogonal to the dipole but when we consider only maps that show exactly the same correlation among the multipoles as in the observed WMAP 5yr ILC, these multipole vectors are unlikely orthogonal to the dipole at $99.7 %$ C.L..