Key points are not available for this paper at this time.
We study the formation and evolution of a sample of Lyman break galaxies in the epoch of reionization by using high-resolution (∼10 pc), cosmological zoom-in simulations part of the SERRA suite. In SERRA, we follow the interstellar medium thermochemical non-equilibrium evolution and perform on-the-fly radiative transfer of the interstellar radiation field (ISRF). The simulation outputs are post-processed to compute the emission of far infrared lines (C II, N II, and O III). At z = 8, the most massive galaxy, `Freesia', has an age t_ ∼eq 409 Myr, stellar mass M⋆ ≃ 4. 2 × 109M⊙, and a star formation rate (SFR), SFR∼eq 11. 5 M⊙ yr^-1, due to a recent burst. Freesia has two stellar components (A and B) separated by ≃ 2. 5 kpc; other 11 galaxies are found within 56. 9 ± 21. 6 kpc. The mean ISRF in the Habing band is G = 7. 9 G₀ and is spatially uniform; in contrast, the ionization parameter is U = 2^+20-₂ × 10^-3, and has a patchy distribution peaked at the location of star-forming sites. The resulting ionizing escape fraction from Freesia is fₑsc∼eq 2{ per cent}. While C II emission is extended (radius 1. 54 kpc), O III is concentrated in Freesia-A (0. 85 kpc), where the ratio Σ O III/Σ C II≃ 10. As many high-z galaxies, Freesia lies below the local C II-SFR relation. We show that this is the general consequence of a starburst phase (pushing the galaxy above the Kennicutt-Schmidt relation) that disrupts/photodissociates the emitting molecular clouds around star-forming sites. Metallicity has a sub-dominant impact on the amplitude of C II-SFR deviations.
Pallottini et al. (Mon,) studied this question.