Do galaxy global relationships emerge from local ones? The SDSS IV MaNGA surface mass density-metallicity relation

TL;DR

This study reveals a strong local correlation between stellar surface mass density and gas metallicity in disk galaxies, which can explain global metallicity trends and gradients, emphasizing the importance of local properties in galaxy evolution.

Contribution

It demonstrates that the local surface density-metallicity relation is fundamental and can reproduce global galaxy metallicity characteristics, a novel insight into galaxy chemical evolution.

Findings

The $ m \Sigma_*-Z$ relation is tight and spans three orders of magnitude in surface density.

This local relation can reproduce the global mass-metallicity relation and metallicity gradients.

The relation is largely independent of total stellar mass and sSFR, except at low mass and high sSFR.

Abstract

We present the stellar surface mass density {\it vs.} gas metallicity ($\Sigma_*-Z$) relation for more than 500,000 spatially-resolved star-forming resolution elements (spaxels) from a sample of 653 disk galaxies included in the SDSS IV MaNGA survey. We find a tight relation between these local properties, with higher metallicities as the surface density increases. This relation extends over three orders of magnitude in the surface mass density and a factor of four in metallicity. We show that this local relationship can simultaneously reproduce two well-known properties of disk galaxies: their global mass-metallicity relationship {\it and} their radial metallicity gradients. We also find that the $\Sigma_* - Z$ relation is largely independent of the galaxy's total stellar mass and specific star-formation rate (sSFR), except at low stellar mass and high sSFR. These results suggest that in the present-day universe local properties play a key role in determining the gas-phase metallicity in typical disk galaxies.