Constraining Sub-Grid Physics with High-Redshift Spatially-Resolved Metallicity Distributions

TL;DR

This study investigates how different stellar feedback models influence the distribution and evolution of metallicity in simulated L* disc galaxies from high redshift to present day, highlighting the importance of feedback in galaxy evolution.

Contribution

It demonstrates that enhanced feedback models produce flatter, more invariant metallicity gradients and reduce scatter in age-metallicity relations, providing new insights into feedback effects.

Findings

Enhanced feedback leads to flatter, more stable metallicity gradients.

Enhanced feedback reduces scatter in age-metallicity and [O/Fe]-[Fe/H] relations.

Metallicity distributions show bimodality consistent with previous dwarf galaxy studies.

Abstract

We examine the role of energy feedback in shaping the distribution of metals within cosmological hydrodynamical simulations of L* disc galaxies. While negative abundance gradients today provide a boundary condition for galaxy evolution models, in support of inside-out disc growth, empirical evidence as to whether abundance gradients steepen or flatten with time remains highly contradictory. We made use of a suite of L* discs, realised with and without `enhanced' feedback. All the simulations were produced using the smoothed particle hydrodynamics code Gasoline, and their in situ gas-phase metallicity gradients traced from redshift z~2 to the present-day. Present-day age-metallicity relations and metallicity distribution functions were derived for each system. The `enhanced' feedback models, which have been shown to be in agreement with a broad range of empirical scaling relations, distribute energy and re-cycled ISM material over large scales and predict the existence of relatively `flat' and temporally invariant abundance gradients. Enhanced feedback schemes reduce significantly the scatter in the local stellar age-metallicity relation and, especially, the [O/Fe]-[Fe/H] relation. The local [O/Fe] distribution functions for our L* discs show clear bimodality, with peaks at [O/Fe]=-0.05 and +0.05 (for stars with [Fe/H]>-1), consistent with our earlier work on dwarf discs. Our results with `enhanced' feedback are inconsistent with our earlier generation of simulations realised with `conservative' feedback. We conclude that spatially-resolved metallicity distributions, particularly at high-redshift, offer a unique and under-utilised constraint on the uncertain nature of stellar feedback processes.