Test of consistency between Planck and WMAP

TL;DR

This study compares the Planck and WMAP cosmic microwave background data to assess their consistency, finding no significant tension when allowing amplitude shifts but highlighting potential systematic issues when fixing amplitudes.

Contribution

It introduces a statistical method using Crossing functions to test the consistency of Planck and WMAP data, emphasizing the role of amplitude adjustments in resolving apparent tensions.

Findings

Planck and WMAP data are consistent when allowing amplitude shifts.

Fixing amplitudes leads to >3σ tension, indicating possible systematics.

No significant tension found when considering overall amplitude flexibility.

Abstract

Within the context of the concordance model of cosmology we test the consistency of the angular power spectrum data from WMAP and Planck looking for possible systematics. The best fit concordance model to each observation is used as a mean function along with a Crossing function with an orthogonal basis to fit the data from the other observation searching for any possible deviation. We report that allowing an overall amplitude shift in the observed angular power spectra of the two observations, the best fit mean function from Planck data is consistent with WMAP 9 year data but the best fit mean function generated from WMAP-9 data is not consistent with Planck data at the $3\sigma$ level. This is an expected result when there is no clear systematic/tension between two observations and one of them has a considerably higher precision. We conclude that there is no clear tension between Planck and WMAP 9 year angular power spectrum data from a statistical point of view (allowing the overall amplitude shift). Our result highlights the fact that while the angular power spectrum from cosmic microwave background observations is a function of various cosmological parameters, comparing individual parameters might be misleading in the presence of cosmographic degeneracies. Another main result of our analysis is the importance of the overall amplitudes of the observed spectra from Planck and WMAP observations. Fixing the amplitudes at their reported values results in an unresolvable tension between the two observations at more than $3\sigma$ level which can be a hint towards a serious systematic.