2016MNRAS.463..670P

We present new or improved oxygen abundances (O/H) for the nearby Lynx-Cancer void updated galaxy sample. They are obtained via the SAO 6-m telescope spectroscopy (25 objects), or derived from the Sloan Digital Sky Survey spectra (14 galaxies, of which for seven objects O/H values were unknown). For eight galaxies with detected [O III] λ4363 line, O/H values are derived via the direct (T_e) method. For the remaining objects, O/H was estimated via semi-empirical and empirical methods. For all accumulated O/H data for 81 galaxies of this void (with 40 of them derived via T_e method), their relation 'O/H versus M_B' is compared with that for similar late-type galaxies from denser environments (the Local Volume 'reference sample'). We confirm our previous conclusion derived for a subsample of 48 objects: void galaxies show systematically reduced O/H for the same luminosity with respect to the reference sample, in average by 0.2 dex, or by a factor of ∼1.6. Moreover, we confirm the fraction of ∼20 per cent of strong outliers, with O/H of two to four times lower than the typical values for the 'reference' sample. The new data are consistent with the conclusion on the slower evolution of the main void galaxy population. We obtained Hα velocity for the faint optical counterpart of the most gas-rich (M(H I)/L_B = 25) void object J0723+3624, confirming its connection with the respective H I blob. For similar extremely gas-rich dwarf J0706+3020, we give a tentative O/H ∼(O/H)_☉/45. In Appendix T_e method.