FOREVER22: Gas and metal outflow from massive galaxies in protocluster regions

TL;DR

This study uses the FOREVER22 simulation to analyze gas and metal outflows from massive galaxies in protocluster regions at high redshift, revealing how outflow properties depend on halo mass and redshift.

Contribution

It provides new insights into the dependence of gas and metal outflows on halo mass and redshift in massive protocluster galaxies at high redshift.

Findings

Mass loading factor varies with halo mass, reaching 9.2 for $10^{11} M_\u2297$ halos.

Outflow velocity decreases rapidly beyond $10^{12.5} M_\u2297$, leading to fountain flows.

Massive halos at $z=3$ are inefficient metal enrichment sources beyond virial radii.

Abstract

We study gas and metal outflow from massive galaxies in protocluster regions at $z=3-9$ by using the results of the FOREVER22 simulation project. Our simulations contain massive haloes with $M_{\rm h} \gtrsim 10^{13}~\rm M_{\odot}$, showing high star formation rates of $> 100~\rm M_{\odot}~yr^{-1}$ and hosting supermassive black holes with $M_{\rm BH} \gtrsim 10^{8}~\rm M_{\odot}$. We show that the mass loading factor ($\eta_{\rm M}$) sensitively depends on the halo mass and it is $\eta_{\rm M} = 1.2~(9.2)$ for $M_{\rm h} = 10^{13}~(10^{11})~\rm M_{\odot}$. Once the halo mass exceeds $\sim 10^{12.5}~\rm M_{\odot}$, the outflow velocity of the gas rapidly decreases near a virial radius, and the gas returns to a galactic centre finally as a fountain flow. Also, the metal inflow and outflow rates sensitively depend on the halo mass and redshift. At $z=3$, the inflow rate becomes larger than the outflow one if $M_{\rm h} \gtrsim 10^{13.0}~\rm M_{\odot}$. Thus, we suggest that massive haloes cannot be efficient metal enrichment sources beyond virial radii that will be probed in future observations, e.g., studies of metal absorption lines with the Prime Focus Spectrograph on the Subaru telescope.