The Parameter-Level Performance of Covariance Matrix Conditioning in Cosmic Microwave Background Data Analyses

Understand

Empirical estimates of the band power covariance matrix are commonly used in cosmic microwave background (CMB) power spectrum analyses.

• While this approach easily captures correlations in the data, noise in the resulting covariance estimate can systematically bias the parameter fitting.
• Conditioning the estimated covariance matrix, by applying prior information on the shape of the eigenvectors, can reduce these biases and ensure the recovery of robust parameter constraints.
• In this work, we use simulations to benchmark the performance of four different conditioning schemes, motivated by contemporary CMB analyses.