Contribution of HIEROs to the galaxy stellar mass function in SPRITZ at z > 4 (red line). The grey and red shaded areas include the errors of the initial luminosity functions used to derive simulated galaxies and the uncertainties due to the high-z extrapolation (z > 3). The observed stellar mass function for HIEROs measured by Wang et al. (2016) at 4.5 < z < 5.5 is reported in both panels as filled orange squares.