Two-point correlation function ρ_p(r) for the peaks in Fig. 3d. The inter-point distance r is in pixels units. The two red lines define the 95% confidence band. They were obtained by means of a bootstrap method based on the 95% percentile envelopes of the two-point correlation functions obtained from 1000 resampled sets of peaks with the same spatial coordinates as in the original signal but whose values were randomly permuted.