The Impact of Outflows driven by Active Galactic Nuclei on Metals in and around Galaxies

TL;DR

This study uses high-resolution simulations to show that AGN-driven outflows significantly enrich galaxy halos and the intergalactic medium with metals, matching recent X-ray observations and highlighting the role of AGN feedback in galaxy evolution.

Contribution

It demonstrates that AGN feedback drives metal-enriching outflows that extend beyond galaxy halos, providing detailed predictions consistent with observations.

Findings

AGN feedback flattens metal profiles in halos

Simulations with AGN have 2.5 times higher iron abundance

Most metals ejected by AGN winds end beyond the halo virial radius

Abstract

Metals in the hot gaseous halos of galaxies encode the history of star formation as well as the feedback processes that eject metals from the galaxies. X-ray observations suggest that massive galaxies have extended distributions of metals in their gas halos. We present predictions for the metal properties of massive galaxies and their gaseous halos from recent high resolution zoom-in simulations that include mechanical and radiation driven feedback from Active Galactic Nuclei (AGN). In these simulations, AGN launch high-velocity outflows, mimicking observed broad absorption line winds. By comparing two sets of simulations with and without AGN feedback, we show that our prescription for AGN feedback is capable of driving winds and enriching halo gas `inside-out' by spreading centrally enriched metals to the outskirts of galaxies, into the halo and beyond. The metal (iron) profiles of halos simulated with AGN feedback have a flatter slope than those without AGN feedback, consistent with recent X-ray observations. The predicted gas iron abundance of group scale galaxies simulated with AGN feedback is $Z_{\rm Fe} = 0.23$ $Z_{\rm Fe,\odot}$ at $0.5 r_{500}$, which is 2.5 times higher than that in simulations without AGN feedback. In these simulations, AGN winds are also important for the metal enrichment of the intergalactic medium, as the vast majority of metals ejected from the galaxy by AGN-driven winds end up beyond the halo virial radius.