High-redshift Halo–Galaxy Connection via Constrained Simulations

Abstract The evolution of halos with masses around M h ≈ 10 11 M ⊙ and M h ≈ 10 12 M ⊙ at redshifts z > 9 is examined using constrained N -body simulations. The average specific mass accretion rates, M ̇ h / M h , exhibit minimal mass dependence and generally agree with existing literature. Individual halo accretion histories, however, vary substantially. About one-third of simulations reveal an increase in M ̇ h around z ≈ 13. Comparing simulated halos with observed galaxies having spectroscopic redshifts, we find that for galaxies at z ≳ 9, the ratio between observed star formation rate and M ̇ h is approximately 2%. This ratio remains consistent for the stellar-to-halo mass ratio (SHMR) but only for z ≳ 10. At z ≃ 9, the SHMR is notably lower by a factor of a few. At z ≳ 10, there is an agreement between specific star formation rates (sSFRs) and M ̇ h / M h . However, at z ≃ 9, observed sSFRs exceed simulated values by a factor of 2. It is argued that the mildly elevated SHMR in high- z halos with M h ≈ 10 11 M ⊙ can be achieved by assuming the applicability of the local Kennicutt–Schmidt law and a reduced effectiveness of stellar feedback due to deeper gravitational potential of high- z halos of a fixed mass.