The oxygen abundance gradients in the gas discs of galaxies in the EAGLE simulation

TL;DR

This study uses EAGLE simulations to analyze gas disc oxygen abundance gradients in galaxies, revealing correlations with disc size and merger history, but generally shallower than observed gradients and no strong environmental dependence.

Contribution

It provides new insights into the relationship between oxygen gradients, galaxy properties, and merger history using high-resolution cosmological simulations.

Findings

Median oxygen gradient is -0.011 dex kpc^-1, shallower than observed.

Shallower gradients correlate with larger gas disc sizes.

Positive gradients are found in about 40% of gas discs, more common in low-mass galaxies.

Abstract

We use the EAGLE simulations to study the oxygen abundance gradients of gas discs in galaxies within the stellar mass range [10^9.5, 10^10.8]Mo at z=0. The estimated median oxygen gradient is -0.011 (0.002) dex kpc^-1, which is shallower than observed. No clear trend between simulated disc oxygen gradient and galaxy stellar mass is found when all galaxies are considered. However, the oxygen gradient shows a clear correlation with gas disc size so that shallower abundance slopes are found for increasing gas disc sizes. Positive oxygen gradients are detected for ~40 per cent of the analysed gas discs, with a slight higher frequency in low mass galaxies. Galaxies that have quiet merger histories show a positive correlation between oxygen gradient and stellar mass, so that more massive galaxies tend to have shallower metallicity gradients. At high stellar mass, there is a larger fraction of rotational-dominated galaxies in low density regions. At low stellar mass, non-merger galaxies show a large variety of oxygen gradients and morphologies. The normalization of the disc oxygen gradients in non-merger galaxies by the effective radius removes the trend with stellar mass. Conversely, galaxies that experienced mergers show a weak relation between oxygen gradient and stellar mass. Additionally, the analysed EAGLE discs show no clear dependence of the oxygen gradients on local environment, in agreement with current observational findings.