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