Validation of the Xpure power spectrum estimator for thermal dust (left panel) and synchrotron (right panel) Gaussian simulations. Gray histograms are obtained from the B-mode power spectra estimation of the input simulated maps in the multipole bin centered at ℓ ≃ 80 in the 352 considered sky regions. Black curves represent the expected Gaussian distribution centered on the mean value of the input spectra from which simulated maps are computed, and with variance defined as in Eq. (1).