The influence of galaxy surface brightness on the mass-metallicity relation

TL;DR

This study investigates how galaxy surface brightness influences the mass-metallicity relation, revealing that lower surface brightness galaxies tend to have lower metallicity independent of gas content, especially in low-mass galaxies.

Contribution

The paper provides spatially-resolved analysis showing surface brightness affects metallicity beyond gas content, and uses chemical models to explore inflow and outflow differences.

Findings

Lower surface brightness galaxies have lower metallicity at fixed stellar mass.

Lower surface brightness galaxies experience stronger gas inflow than higher surface brightness counterparts.

The surface brightness effect is more pronounced in low-mass galaxies.

Abstract

We study the effect of surface brightness on the mass-metallicity relation using nearby galaxies whose gas content and metallicity profiles are available. Previous studies using fiber spectra indicated that lower surface brightness galaxies have systematically lower metallicity for their stellar mass, but the results were uncertain because of aperture effect. With stellar masses and surface brightnesses measured at WISE W1 and W2 bands, we re-investigate the surface brightness dependence with spatially-resolved metallicity profiles and find the similar result. We further demonstrate that the systematical difference cannot be explained by the gas content of galaxies. For two galaxies with similar stellar and gas masses, the one with lower surface brightness tends to have lower metallicity. Using chemical evolution models, we investigate the inflow and outflow properties of galaxies of different masses and surface brightnesses. We find that, on average, high mass galaxies have lower inflow and outflow rates relative to star formation rate. On the other hand, lower surface brightness galaxies experience stronger inflow than higher surface brightness galaxies of similar mass. The surface brightness effect is more significant for low mass galaxies. We discuss implications on the different inflow properties between low and high surface brightness galaxies, including star formation efficiency, environment and mass assembly history.