High-redshift halo-galaxy connection via constrained simulations

Abstract

The evolution of halos with masses around $M_\textrm{h} \approx 10^{11}\; \textrm{M}_\odot$ and $M_\textrm{h} \approx 10^{12}\; \textrm{M}_\odot$ at redshifts $z>9$ is examined using constrained N-body simulations. {The average specific mass accretion rates, $\dot{M}_\textrm{h} / M_\textrm{h}$, 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 $\dot{M}_\textrm{h}$ around $z\approx 13$. Comparing simulated halos with observed galaxies having spectroscopic redshifts, we find that for galaxies at $z\gtrsim9$, the ratio between observed star formation rate (SFR) and $\dot{M}_\textrm{h}$ is approximately $2\%$. This ratio remains consistent for the stellar-to-halo mass ratio (SHMR) but only for $z\gtrsim 10$. At $z\simeq 9$, the SHMR is notably lower by a factor of a few. At $z\gtrsim10$, there is an agreement between specific star formation rates (sSFRs) and $\dot{M}_\textrm{h} / M_\textrm{h}$. However, at $z\simeq 9$, observed sSFRs exceed simulated values by a factor of two. It is argued that the mildly elevated SHMR in high-$z$ halos with $M_\textrm{h} \approx 10^{11} M_{\odot}$, 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.