Determining the large-scale environmental dependence of gas-phase metallicity in dwarf galaxies

TL;DR

This study compares the gas-phase metallicity of dwarf galaxies in cosmic voids and denser regions, finding minimal environmental influence but noting fewer extremely metal-poor galaxies in voids.

Contribution

It provides the first large-sample spectroscopic comparison of metallicities in void and dense-region dwarf galaxies using SDSS data.

Findings

Little difference in metallicity between void and dense-region dwarf galaxies

Fewer extremely metal-poor dwarf galaxies in voids

Environmental impact on chemical evolution appears minimal

Abstract

We study how the cosmic environment affects galaxy evolution in the Universe by comparing the metallicities of dwarf galaxies in voids with dwarf galaxies in more dense regions. Ratios of the fluxes of emission lines, particularly those of the forbidden [O III] and [S II] transitions, provide estimates of a region's electron temperature and number density. From these two quantities and the emission line fluxes [O II] 3727, [O III] 4363, and [O III] 4959,5007, we estimate the abundance of oxygen with the Direct Te method. We estimate the metallicity of 42 blue, star-forming void dwarf galaxies and 89 blue, star-forming dwarf galaxies in more dense regions using spectroscopic observations from the Sloan Digital Sky Survey Data Release 7, as re-processed in the MPA-JHU value-added catalog. We find very little difference between the two sets of galaxies, indicating little influence from the large-scale environment on their chemical evolution. Of particular interest are a number of extremely metal-poor dwarf galaxies that are less prevalent in voids than in the denser regions.