Study of galaxies in the Eridanus void. Sample and oxygen abundances

TL;DR

This study analyzes the properties of 66 galaxies in the Eridanus void, focusing on their metallicity and gas content, and compares these with galaxies in denser environments to understand environmental effects on galaxy evolution.

Contribution

It provides the first systematic analysis of oxygen abundances in Eridanus void galaxies, including new spectroscopic measurements and a comparative study with galaxies in denser regions.

Findings

Void galaxies have significantly lower average metallicity than their counterparts in denser environments.

The study presents new oxygen abundance measurements for 23 galaxies using SALT and BTA telescopes.

Comparison with control samples confirms environmental influence on galaxy chemical evolution.

Abstract

We present a sample of 66 galaxies belonging to the equatorial part (Dec.= -7$^o$, +7$^o$) of the large so called Eridanus void (after Fairall 1998). The void galaxies are selected as to be separated from the luminous galaxies ($M_{\rm B} < M_{\rm B}^{*} +1$), delineating the void, by more than 2 Mpc. Our main goal is to study systematically the evolutionary parameters of the void sample (metallicity and gas content) and to compare the void galaxy properties with their counterparts residing in denser environments. Besides the general galaxy parameters, compiled mainly from the literature, we present the results of dedicated observations to measure the oxygen abundance O/H in HII-regions of 23 void galaxies obtained with the 11-m SALT telescope (SAAO) and the 6-m BTA telescope (SAO), as well as the O/H estimates derived from the analysis of the SDSS DR12 spectra for 3 objects. We compiled all available data on O/H in 36 these void galaxies, including those for 11 galaxies available in the literature (for one object both SDSS and SALT spectra were used), and analyze this data in relation to galaxy luminosity ($\log$(O/H) versus $M_{\rm B}$). Comparing them with the control sample of similar type galaxies from the Local Volume, we find clear evidence for a substantially lower average metallicity of the Eridanus void galaxies. This result matches well the conclusions of our recent similar study for galaxies in the Lynx-Cancer void.