SDSS-IV MaNGA: Environmental dependence of gas metallicity gradients in local star-forming galaxies

TL;DR

This study investigates how environment influences gas metallicity and star formation in local galaxies, finding that low-mass satellites show environmental effects on their metallicity gradients and star formation, explained by gas inflow processes.

Contribution

It provides spatially resolved analysis of metallicity and star formation gradients in galaxies, highlighting environmental effects on low-mass satellites and proposing a gas inflow model.

Findings

Low-mass satellite galaxies have flatter metallicity gradients in dense environments.

Star formation surface density gradients steepen with environmental density.

A gas inflow model explains the observed gradient patterns.

Abstract

Within the standard model of hierarchical galaxy formation in a {\Lambda}CDM Universe, the environment of galaxies is expected to play a key role in driving galaxy formation and evolution. In this paper we investigate whether and how the gas metallicity and the star formation surface density ({\Sigma}_SFR) depend on galaxy environment. To this end we analyse a sample of 1162 local, star-forming galaxies from the galaxy survey Mapping Nearby Galaxies at APO (MaNGA). Generally, both parameters do not show any significant dependence on environment. However, in agreement with previous studies, we find that low-mass satellite galaxies are an exception to this rule. The gas metallicity in these objects increases while their {\Sigma}SFR decreases slightly with environmental density. The present analysis of MaNGA data allows us to extend this to spatially resolved properties. Our study reveals that the gas metallicity gradients of low-mass satellites flatten and their {\Sigma}SFR gradients steepen with increasing environmental density. By extensively exploring a chemical evolution model, we identify two scenarios that are able to explain this pattern: metal-enriched gas accretion or pristine gas inflow with varying accretion timescales. The latter scenario better matches the observed {\Sigma}SFR gradients, and is therefore our preferred solution. In this model, a shorter gas accretion timescale at larger radii is required. This suggests that 'outside-in quenching' governs the star formation processes of low-mass satellite galaxies in dense environments.