Normalized histograms and quantile-quantile plots of post-subtraction residual noise (from the 821 spectral channels of the median cube of the post-subtraction residuals of PDS70 images indicated in App. C, with our proposed method following the parameters indicated in Tab. 1). Each monochromatic image is separated into concentric rings (Andres 1994) grouped by 3 to distinguish distributions by separation at the center. Due to stellar residuals and possibly photon noise, the noise standard deviation is greater in the center, as shown in the figure on the left, and its distribution deviates from a Gaussian distribution, as shown in the figure on the right. On the contrary, as the separation increases, the standard deviation decreases and the distribution approaches a Gaussian distribution.