Influence of the size A (given in pixels and displayed as a disk at the scale of the field of view) of the region over which the spectral covariances are estimated. The S/N_ℓ maps are combined assuming the spectrum shown in (g), for whitening matrices obtained from each estimate of the spectral covariance. From a to f: combined maps wwS/N and the empirical distribution of wwS/N under ℋ₀ are shown side by side.