The Baryon Cycle at High Redshifts: Effects of Galactic Winds on Galaxy Evolution in Overdense and Average Regions

TL;DR

This study uses high-resolution cosmological simulations to examine how galactic winds influence galaxy evolution during reionization, highlighting environment-dependent effects and the importance of wind modeling.

Contribution

It introduces and compares different outflow prescriptions in simulations, demonstrating the impact of wind models on galaxy properties and intergalactic medium state at high redshift.

Findings

Overdensity accelerates structure evolution and affects low-mass galaxy populations.

Variable wind models better reproduce observed galaxy relations.

Wind models significantly influence the distribution of hot, metal-rich gas in the IGM.

Abstract

We employ high-resolution cosmological zoom-in simulations focusing on a high-sigma peak and an average cosmological field at $z\sim 6-12$, in order to investigate the influence of environment and baryonic feedback on galaxy evolution in the reionization epoch. Strong feedback, e.g., galactic winds, caused by elevated star formation rates (SFRs) is expected to play an important role in this evolution. We compare different outflow prescriptions: (i) constant wind velocity (CW), (ii) variable wind scaling with galaxy properties (VW), and (iii) no outflows (NW). The overdensity leads to accelerated evolution of dark matter and baryonic structures, absent in the "normal" region, and to shallow galaxy stellar mass functions at the low-mass end. Although CW shows little dependence on both environments, the more physically motivated VW model does exhibit this effect. In addition, VW can reproduce the observed specific SFR (sSFR) and the sSFR-stellar mass relation, which CW and NW fail to satisfy simultaneously. Winds also differ substantially in affecting the state of the intergalactic medium (IGM). The difference lies in volume-filling factor of hot, high-metallicity gas which is near unity for CW, while it remains confined in massive filaments for VW, and locked up in galaxies for NW. Such gas is nearly absent in the normal region. Although all wind models suffer from deficiencies, the VW model seems to be promising in correlating the outflow properties to those of host galaxies. Further constraints on the state of the IGM at high-$z$ are needed to separate different wind models.