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

We study the effect of the gas accretion rate (M_accr) on the radial gas metallicity profile (RMP) of galaxies using the eagle cosmological hydrodynamic simulations, focusing on central galaxies of stellar mass M_* ≳ 10⁹ M_ʘ at z ≤ 1. We find clear relations between M_accr and the slope of the RMP (measured within an effective radius), where higher M_accr are associated with more negative slopes. The slope of the RMPs depends more strongly on M_accr than on stellar mass, star formation rate (SFR), or gas fraction, suggesting M_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 M_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.