False positive rate as functions of redshift and f_Hα+[N II] for Flagship2. The plot allows us to identify the origin of non-targets that enter the selected samples. The solid blue, dashed orange, and dotted purple curves, respectively, correspond to the neural networks trained with Euclid photometry, Euclid plus morphological data, and Euclid plus ground-based photometry. The dash-dotted red line is the false positive rate of the photo-z selection. Top: False positive rate as a function of z. The green shaded area marks the target redshift range. Bottom: False positive rate as a function of f_Hα+[N II]. The green shaded area corresponds to the Hα limiting flux. There is a peak in the false positive rate just below the flux limit used to define the target sample, although we note that these galaxies can still give correct redshift measurements.