Legacy of star formation in the pre-reionization universe

We utilize GIZMO, coupled with newly developed sub-grid models for Population III (Pop III) and Population II (Pop II), to study the legacy of star formation in the prereionization Universe. We find that the Pop II star formation rate density (SFRD), produced in our simulation (similar to 10(-2) M-circle dot yr(-1) Mpc(-3) at z similar or equal to 10), matches the total SFRD inferred from observations within a factor of < 2 at 7 less than or similar to z less than or similar to 10. The Pop III SFRD, however, reaches a plateau at similar to 10(-3) M-circle dot yr(-1) Mpc(-3) by z approximate to 10, remaining largely unaffected by the presence of Pop II feedback. At z = 7.5, similar to 20 per cent of Pop III star formation occurs in isolated haloes that have never experienced any Pop II star formation (i.e. primordial haloes). We predict that Pop III-only galaxies exist at magnitudes M-UV greater than or similar to -11, beyond the limits for direct detection with the James Webb Space Telescope. We assess that our stellar mass function (SMF) and UV luminosity function (UVLF) agree well with the observed low mass/faint-end behaviour at z = 8 and 10. However, beyond the current limiting magnitudes, we find that both our SMF and UVLF demonstrate a deviation/turnover from the expected power-law slope (M-UV,M-turn = -13.4 +/- 1.1 at z = 10). This could impact observational estimates of the true SFRD by a factor of 2(10) when integrating to M-UV = -12 (-8) at z similar to 10, depending on integration limits. Our turnover correlates well with the transition from dark matter haloes dominated by molecular cooling to those dominated by atomic cooling, for a mass M-halo approximate to 10(8) M-circle dot at z similar or equal to 10.