SDSS-IV/MaNGA: Can Impulsive Gaseous Inflows Explain Steep Oxygen Abundance Profiles and Anomalously Low-Metallicity Regions?

Abstract

Gaseous inflows are necessary suppliers of galaxies’ star-forming fuel, but are difficult to characterize at the survey scale. We use integral-field spectroscopic measurements of gas-phase metallicity and single-dish radio measurements of total atomic gas mass to estimate the magnitude and frequency of gaseous inflows incident on star-forming galaxies. We reveal a mutual correlation between steep oxygen abundance profiles between 0.25 and 1.5 R e , increased variability of metallicity between 1.25 and 1.75 R e , and elevated H i content at fixed total galaxy stellar mass. Employing a simple but intuitive inflow model, we find that galaxies with total stellar mass less than 10 10.1 M ⊙ have local oxygen abundance profiles consistent with reinvigoration by inflows. Approximately 10%–25% of low-mass galaxies possess signatures of recent accretion, with estimated typical enhancements of approximately 10%–90% in local gas mass surface density. Higher-mass galaxies have limited evidence for such inflows. The large diversity of H i mass implies that inflow-associated gas ought to reside far from the star-forming disk. We therefore propose that a combination of high H i mass, steep metallicity profile between 0.25 and 1.5 R e , and wide metallicity distribution function between 1.25 and 1.75 R e be employed to target possible hosts of inflowing gas for high-resolution radio follow-up.