Metal Transport to the Gaseous Outskirts of Galaxies

TL;DR

This study investigates metal distribution in the outskirts of nearby galaxies, revealing flat oxygen abundance gradients out to large radii, which impacts our understanding of galaxy evolution.

Contribution

It provides the first convincing evidence of flat metallicity gradients in galaxy outskirts across diverse systems, using new spectroscopic measurements.

Findings

Oxygen abundance gradients extend to 2.5 times the optical radius.

Metallicity distributions are flat in galaxy outskirts.

Implications for galaxy chemodynamical evolution.

Abstract

We present a search for outlying HII regions in the extended gaseous outskirts of nearby (D < 40 Mpc) galaxies, and subsequent multi-slit spectroscopy used to obtain the HII region nebular oxygen abundances. The galaxies in our sample have extended HI disks and/or interaction-related HI features that extend well beyond their primary stellar components. We report oxygen abundance gradients out to 2.5 times the optical radius for these galaxies which span a range of morphologies and masses. We analyze the underlying stellar and neutral HI gas distributions in the vicinity of the HII regions to understand the physical processes that give rise to the observed metal distributions in galaxies. These measurements, for the first time, convincingly show flat abundance distributions out to large radii in a wide variety of systems, and have broad implications for galaxy chemodynamical evolution.