The metallicity of void dwarf galaxies

TL;DR

This study compares the chemical properties of dwarf galaxies in voids and average environments, finding no significant differences, which suggests internal processes dominate their evolution regardless of environment.

Contribution

It provides the first direct comparison of void and isolated dwarf galaxy metallicities, challenging the assumption that environment significantly influences their chemical evolution.

Findings

Void dwarf galaxies have similar metallicities to isolated dwarfs.

External gas accretion appears limited in influencing chemical evolution.

Internal secular processes mainly drive dwarf galaxy evolution.

Abstract

The current Lambda CDM cosmological model predicts that galaxy evolution proceeds more slowly in lower density environments, suggesting that voids are a prime location to search for relatively pristine galaxies that are representative of the building blocks of early massive galaxies. To test the assumption that void galaxies are more pristine, we compare the evolutionary properties of a sample of dwarf galaxies selected specifically to lie in voids with a sample of similar isolated dwarf galaxies in average density environments. We measure gas-phase oxygen abundances and gas fractions for eight dwarf galaxies (M_r > -16.2), carefully selected to reside within the lowest density environments of seven voids, and apply the same calibrations to existing samples of isolated dwarf galaxies. We find no significant difference between these void dwarf galaxies and the isolated dwarf galaxies, suggesting that dwarf galaxy chemical evolution proceeds independent of the large-scale environment. While this sample is too small to draw strong conclusions, it suggests that external gas accretion is playing a limited role in the chemical evolution of these systems, and that this evolution is instead dominated mainly by the internal secular processes that are linking the simultaneous growth and enrichment of these galaxies.