Metal-poor dwarf galaxies in the sigrid galaxy sample. I. H II region observations and chemical abundances

Abstract

In this paper we present the results of observations of 17 HII regions in thirteen galaxies from the SIGRID sample of isolated gas-rich irregular dwarf galaxies. The spectra of all but one of the galaxies exhibit the auroral [O III] 4363 Å line, from which we calculate the electron temperature, Te, and gas-phase oxygen abundance. Five of the objects are blue compact dwarf galaxies, of which four have not previously been analyzed spectroscopically. We include one unusual galaxy which exhibits no evidence of the [NII] λλ 6548, 6584 Å lines, suggesting a particularly low metallicity ( Z⊗ > 0.15.