Observational properties of the galaxy samples used throughout this work. Upper panel: magnitude-redshift distribution of the COSMOS2020 galaxy sample used to train the SOM (blue color map with hexagonal pixels) after pre-selection at K_s <  24.8 and log(M/M_⊙)> 8.5. Individual sources with a 5σ detection in MIPS are overplotted as orange dots. Lower panel: photometric redshift distribution of the COSMOS2020 training set (blue histogram) and the SXDF2018 target sample (green). These data sets are described in Sects. 2.1 and 2.2.