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

Abstract

We present a sample of 66 galaxies belonging to the equatorial part (Dec.= -7 • , +7 • ) of the large so called Eridanus void (after Fairall 1998). The void galaxies are selected as to be separated from the luminous galaxies (M B < M * 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 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.

The Leoncino Dwarf Galaxy: Exploring the Low-metallicity End of the Luminosity–Metallicity and Mass–Metallicity Relations*

“…To place the properties of Leoncino in a broader context, we present a comparison of the oxygen abundances of low-mass galaxies as a function of absolute optical luminosity. We include galaxies in typical field environments in the Local Volume from Berg et al (2012), galaxies in void environments from Pustilnik et al (2016) and Kniazev et al (2018), and XMP galaxies from various studies.…”

“…Again, we limit our comparison sample to those with oxygen abundances measured using the direct method. To simplify the plot, we now show the data from the LVL galaxies in Berg et al (2012) and the void galaxies from Pustilnik et al (2016) and Kniazev et al (2018) as transparent black and cyan points, respectively, with their best-fitting lines and dispersions.…”

Low-redshift lowest-metallicity star-forming galaxies in the SDSS DR14

“…al. (2016) and Kniazev et al (2018) derived 12 + logO/H < ∼ 7.35 in nearly a dozen of galaxies in the Lynx-Cancer and Eridanus voids.…”

XMP gas-rich dwarfs in nearby voids: results of SALT spectroscopy

“…Positions of 22 NVG XMP candidates studied with SALT, plus one known from the literature (J2104-0035) and nine candidates from the BTA part of the program (a paper in preparation), in the diagram 12+log(O/H) versus absolute blue magnitude M B (green rhombs) along with similar data for the Lynx-Cancer (black octagons,Pustilnik et al 2016) and Eridanus (red triangles,Kniazev et al 2018) voids. The solid line shows the relation between 12+log(O/H) and M B for the reference sample of the Local Volume late type galaxies fromBerg et al (2012), extrapolated for M B > -10.5.…”