SDSS-IV/MaNGA: Can impulsive gaseous inflows explain steep oxygen abundance profiles \& anomalously-low-metallicity regions?

TL;DR

This study investigates how impulsive gaseous inflows influence the metallicity profiles and low-metallicity regions in star-forming galaxies, using spectroscopic and radio data to identify inflow signatures and their effects.

Contribution

It introduces an analysis linking metallicity profile features and HI content to recent gaseous inflows, providing observational evidence and a method to identify inflow-hosting galaxies.

Findings

Low-mass galaxies show metallicity profiles consistent with recent inflows.

Approximately 10-25% of low-mass galaxies exhibit inflow signatures.

High HI mass and steep metallicity profiles can identify inflow candidates.

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 $0.25-1.5 R_e$, increased variability of metallicity between $1.25-1.75 R_e$, and elevated HI content at fixed total galaxy stellar mass. Employing a simple but intuitive inflow model, we find that galaxies with total stellar mass less than $10^{10.1} {\rm M_{\odot}}$ 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 HI mass implies that inflow-associated gas ought to reside far from the star-forming disk. We therefore propose that a combination of high HI mass, steep metallicity profile between $0.25-1.5 R_e$, and wide metallicity distribution function between $1.25 - 1.75 R_e$ be employed to target possible hosts of inflowing gas for high-resolution radio follow-up.