Properties of the non-target serendipitously detected sources. Top: M_dust vs. L_IR for the non-target serendipitously detected sources in the ALPINE redshift range (4.1 < z < 5.9). The corresponding M_dust was calculated using the same expression as for the ALPINE targets (Eq. (1)). The Bayesian linear fit is shown by the black and light blue lines, which also illustrate the probability distribution of the fit at 1σ confidence level. The resulting best fit is (dispersion dex, Pearson rank coefficient of 0.97, and p-value 10⁻⁵). Bottom: distribution of the L_IR for the target continuum detected (blue histogram, ⟨log() and for the serendipitously detected (red histogram, ⟨log() ALPINE sources. L_IR valuees were estimated using the stacked SED from ALPINE analogues in the COSMOS field from Béthermin et al. (2020).