Large scale alignment anomalies of CMB anisotropies: a new test for residuals applied to WMAP 5yr maps

TL;DR

This paper introduces a new Monte Carlo-based method to test for residual contamination in WMAP 5-year CMB maps by analyzing the alignment of low multipoles, revealing the ILC map as the cleanest among those tested.

Contribution

It presents a novel, mask-independent test for residuals in CMB maps based on alignment anomalies, applicable to current and future experiments.

Findings

WMAP-ILC map is the least contaminated by residuals.

The method effectively distinguishes residual contamination through probability distribution analysis.

Applicable to various masks and future CMB data analyses.

Abstract

We analyze the alignment of the low multipoles (quadrupole and octupole) of various maps of the WMAP 5yr release: the CMB maps obtained with ILC and MCMC methods, the CMB map in the V band after foreground reduction, and, for comparison, the (not cleaned) V band map. We study how much this alignment is polluted by residuals on the Galactic region. Among the considered maps, the WMAP-ILC turns out to be the most clean map from the point of view of the proposed test. This result has been found studying the redistribution (due to the masking process) of each bin of the probability distribution functions of the alignment estimators. By construction, our method, feasible through Monte Carlo simulations, works for any possible mask adopted in the analysis of data from current and forthcoming CMB anisotropy experiments and it can only exclude that the considered map is clean.