HIEROs selection, redshift and extinction in the Simulated Euclid Deep Survey Catalogue. Left: H_E − [4.5] versus J_E − H_E diagram for the simulated Euclid Deep survey catalogue (5σ depth) colour-coded by redshift. Top right: Redshift distribution of red HIEROs (red), blue HIEROs (blue), and galaxies with H_E − [4.5]< 2.25 (grey). Bottom right: Optical extinction distribution of red HIEROs (red) and blue HIEROs (blue). We normalised each histogram to obtain an area equal to unity.