Check for the applicability of the proposed detection procedure for two different situations (see text). Left panel: histogram H(z) vs. ψ(z) from Eq. (10) for a numerical realization of a zero-mean unit-variance Gaussian random field with autocorrelation given by a circular Gaussian with dispersion set to three pixels. Right panel: as in the left panel but with the dispersion of the Gaussian autocorrelation function set to one pixel.