High-redshift halo-galaxy connection via constrained simulations

TL;DR

This study uses constrained simulations to explore the high-redshift halo-galaxy connection, revealing how halo growth and star formation relate at redshifts above 9, with implications for galaxy formation models.

Contribution

It provides new insights into the evolution of high-redshift halos and their star formation rates, comparing simulations with observations to refine galaxy formation theories.

Findings

Average halo accretion rates agree with literature but vary individually.

Observed star formation rates are about 2% of halo mass accretion rates at z>9.

The stellar-to-halo mass ratio is lower at z≈9 and aligns with specific star formation rates at z>10.

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.