The effect of gas accretion on the radial gas metallicity profile of simulated galaxies

TL;DR

This study uses cosmological simulations to show that the gas accretion rate significantly influences the radial metallicity profile of galaxies, more so than stellar mass or star formation rate.

Contribution

It demonstrates that gas accretion rate is a fundamental driver of the metallicity profile slope, revealing new insights into galaxy evolution mechanisms.

Findings

Higher gas accretion rates lead to more negative metallicity profile slopes.

The RMP slope correlates more strongly with accretion rate than with stellar mass.

Galaxies with higher gas fractions and SFRs tend to have steeper metallicity gradients.

Abstract

We study the effect of the gas accretion rate ($\dot M_{\rm accr}$) on the radial gas metallicity profile (RMP) of galaxies using the EAGLE cosmological hydrodynamic simulations, focusing on central galaxies of stellar mass $M_\star \gtrsim 10^9 \, {\rm M_\odot}$ at $z \le 1$. We find clear relations between $\dot M_{\rm accr}$ and the slope of the RMP (measured within an effective radius), where higher $\dot M_{\rm accr}$ are associated with more negative slopes. The slope of the RMPs depends more strongly on $\dot M_{\rm accr}$ than on stellar mass, star formation rate or gas fraction, suggesting $\dot M_{\rm accr}$ to be a more fundamental driver of the RMP slope of galaxies. We find that eliminating the dependence on stellar mass is essential for pinning down the properties that shape the slope of the RMP. Although $\dot M_{\rm accr}$ is the main property modulating the slope of the RMP, we find that it causes other correlations that are more easily testable observationally: at fixed stellar mass, galaxies with more negative RMP slopes tend to have higher gas fractions and SFRs, while galaxies with lower gas fractions and SFRs tend to have flatter metallicity profiles within an effective radius.