Evolving IMF compared with the Salpeter IMF, and the evolution of the massive fraction with redshift and metallicity. Left: evolving IMF at different absolute metallicities Z = 10⁻² (purple lines), 10⁻³ (orange lines), 10⁻⁴ (green lines) and redshifts z = 5 (dashed lines), 10 (dot-dashed lines), and 15 (solid lines). For clarity, the evolving IMFs at z = 10 and 15 have been displaced by lg(ϕ) = 2 and 4, respectively. Thin black lines show the Salpeter IMF at the depicted redshifts. Right: massive fraction f_massive depicted as a function of redshift z and absolute metallicity Z. The top-left corner shows the evolving IMF developing into the Salpeter IMF, where f_massive = 0.