Testing the effect of galactic feedback on the IGM at z ~ 6 with metal-line absorbers

TL;DR

This study models metal-line absorbers at the end of reionization (z ~ 6) using hydrodynamical simulations to understand how galactic feedback influences metal distribution in the IGM.

Contribution

It compares different feedback schemes and hydro-solvers to assess their impact on metal-line absorber predictions at high redshift.

Findings

O I and C II absorbers are insensitive to feedback variations.

Simulations struggle to reproduce observed C IV and Mg II absorbers.

Harder UV backgrounds improve but do not fully resolve discrepancies.

Abstract

We present models of low- and high-ionization metal-line absorbers (O I, C II, C IV and Mg II) during the end of the reionization epoch, at z ~ 6. Using four cosmological hydrodynamical simulations with different feedback schemes (including the Illustris and Sherwood simulations) and two different choices of hydro-solver, we investigate how the overall incidence rate and equivalent width distribution of metal-line absorbers varies with the galactic wind prescription. We find that the O I and C II absorbers are reasonably insensitive to the feedback scheme. All models, however, struggle to reproduce the observations of C IV and Mg II, which are probing down to lower overdensities than O I and C II at z ~ 6, suggesting that the metals in the simulations are not being transported out into the IGM efficiently enough. The situation is improved but not resolved if we choose a harder (but still reasonable) and/or (locally) increased UV background at z ~ 6.