Low Variance at large scales of WMAP 9 year data

TL;DR

This paper analyzes the variance of WMAP 9-year CMB data at large scales, revealing significant temperature anomalies inconsistent with the $ m{ extLambda CDM}$ model, while polarization remains anomaly-free, and provides new power spectrum estimates.

Contribution

It introduces an optimal estimator for variance analysis and presents new low-resolution power spectrum estimates from WMAP 9-year data.

Findings

Significant temperature variance deviations from $ m{ extLambda CDM}$ at large scales.

No anomalies detected in polarization data.

New optimal estimates of the WMAP 9-year low-resolution power spectra.

Abstract

We use an optimal estimator to study the variance of the WMAP 9 CMB field at low resolution, in both temperature and polarization. Employing realistic Monte Carlo simulation, we find statistically significant deviations from the $\Lambda$CDM model in several sky cuts for the temperature field. For the considered masks in this analysis, which cover at least the 54% of the sky, the WMAP 9 CMB sky and $\Lambda$CDM are incompatible at $ \ge 99.94%$ C.L. at large angles ($>5^\circ$). We find instead no anomaly in polarization. As a byproduct of our analysis, we present new, optimal estimates of the WMAP 9 CMB angular power spectra from the WMAP 9 year data at low resolution.