Direct determination of oxygen abundances in line-emitting star-forming galaxies at intermediate redshift

We present a sample of 22 blue [(B - V)_AB < 0.45], luminous (M_B,AB < -18.9), metal-poor galaxies in the 0.69 < z < 0.88 redshift range, selected from the DEEP2 galaxy redshift survey. Their spectra contain the [O III] λ4363 auroral line, the [O II] λλ3726, 3729 doublet and the strong nebular [O III] λλ4959, 5007 emission lines. The ionized gas-phase oxygen abundances of these galaxies lie between 7.62 < 12 + log O/H < 8.19, I.e., between 1/10 Z_⊙ and 1/3 Z_⊙. We find that galaxies in our sample have comparable metallicities to other intermediate-redshift samples, but are more metal poor than local systems of similar B-band luminosities and star formation activity. The galaxies here show similar properties to the green peas discovered at z ≃ 0.2-0.3, though our galaxies tend to be slightly less luminous.