Consistency tests for Planck and WMAP in the low multipole domain

TL;DR

This study performs consistency tests on Planck and WMAP CMB maps, revealing that WMAP ILC9 is more contaminated than ILC7, and finds no significant systematics in Planck maps based on cross-correlation analysis.

Contribution

It introduces a method to test the consistency of CMB maps by analyzing cross correlations between difference maps and original maps, highlighting contamination issues in WMAP ILC9.

Findings

No significant correlations in Planck maps with difference maps.

Significant contamination detected in WMAP ILC9 map.

ILC7 map shows less contamination than ILC9.

Abstract

Recently, full sky maps from Planck have been made publicly available. In this paper, we do consistency tests for the three Planck CMB sky maps. We assume that the difference between two maps represents the contributions from systematics, noise, foregrounds and other sources, and that a precise representation of the Cosmic Microwave Background should be uncorrelated with it. We investigate the cross correlation in pixel space between the difference maps and the various Planck maps and find no significant correlations, in comparison to 10000 random Gaussian simulated maps. Additionally we investigate the difference map between the WMAP ILC 9 year map and the ILC 7 year map. We perform cross correlations between this difference map, and the ILC9 and ILC7, and find significant correlations only for the ILC9, at more than the 99.99% level. Likewise, a comparison between the Planck NILC map and the WMAP ILC9 map, shows a strong correlation for the ILC9 map with the difference map, also at more than the 99.99% level. Thus the ILC9 appears to be more contaminated than the ILC7, which should be taken into consideration when using WMAP maps for cosmological analyses.