Galaxies in the Cosmic Dawn II simulation

With 4096^3^ particles and cells in a 94Mpc box, it is large enough to model global reionization and its feedback on galaxy formation while resolving all haloes above 10^8^M_{sun}_. Using the same hybrid CPU-GPU code RAMSES-CUDATON as CoDa I in Ocvirk et al. (2016MNRAS.463.1462O), CoDa II modified and re-calibrated the subgrid star-formation algorithm, making reionization end earlier, at z>~6, thereby better matching the observations of intergalactic Lyman-alpha opacity from quasar spectra and electron-scattering optical depth from cosmic microwave background fluctuations.

CoDa II predicts a UV continuum luminosity function in good agreement with observations of high-z galaxies, especially at z=6. As in CoDa I, reionization feedback suppresses star formation in haloes below ~2x10^9^M_{sun}_, though suppression here is less severe, a possible consequence of modifying the star-formation algorithm. Suppression is environment-dependent, occurring earlier (later) in overdense (underdense) regions, in response to their local reionization times.