Star formation histories obtained with PPXF from the spectra of the three objects extracted within an aperture of radius r = 0.4″, corresponding to five XSH pixels. The time x-axis corresponds to the time since the BB, and the vertical solid line in each panel shows the age of the Universe at the redshift of the corresponding object. Black lines show the cumulative stellar mass fraction inferred from the unregularised mass-weighted PPXF fit with the best value of [α/Fe] estimated from line indices (Fig. 6). Green lines instead show the results of the fit performed with the regularization set to the MAX_REGUL. Finally, coloured dashed lines show the impact of performing the fit (with REGUL = 0) using models with different [α/Fe].