Quadratic estimator for CMB cross-correlation

Understand

The Quadratic Maximum Likelihood estimator can be used to reconstruct the Cosmic Microwave Background (CMB) power spectra with minimal error bars.

• Still, it requires an accurate estimate of the datasets noise covariance matrix in order to be corrected for spurious bias.
• We describe an extension of this method to cross-correlation, thus removing noise bias and mitigating the impact of systematic effects, providing they are uncorrelated.
• This estimator is tested on two simulation surveys at large and intermediate angular scales, respectively corresponding to satellite and ground-based CMB experiments.