Metallicities of 0.3<z<1.0 galaxies in the GOODS-North field

We measure nebular oxygen abundances for 204 emission-line galaxies with redshifts 0.3<1.0 in the Great Observatories Origins Deep Survey-North (GOODS-N) field using spectra from the Team Keck Redshift Survey. We also provide an updated analytic prescription for estimating oxygen abundances using the traditional strong emission line ratio, R-23, based on the photoionization models of Kewley & Dopita. We include an analytic formula for very crude metallicity estimates using the [N II](lambda6584)/Halpha ratio. Oxygen abundances for GOODS-N galaxies span the range 8.2less than or equal to12+log (O/H)<9.1, corresponding to metallicities between 0.3 and 2.5 times the solar value. This sample of galaxies exhibits a correlation between rest-frame blue luminosity and gas-phase metallicity (i.e., an L-Z relation), consistent with L-Z correlations of previously studied intermediate-redshift samples. The zero point of the L-Z relation evolves with redshift, in the sense that galaxies of a given luminosity become more metal-poor at higher redshift. Galaxies in luminosity bins -18.5<-21.5 exhibit a decrease in average oxygen abundance by 0.14 +/- 0.05 dex from z=0 to 1. This rate of metal enrichment means that 28%+/- 0.07% of metals in local galaxies have been synthesized since z=1, in reasonable agreement with the predictions based on published star formation rate densities, which show that similar to 38% of stars in the universe have formed during the same interval. The slope of the L-Z relation may evolve, in the sense that the least luminous galaxies at each redshift interval become increasingly metal-poor compared to more luminous galaxies. We interpret this change in slope as evidence for more rapid chemical evolution among the least luminous galaxies (M-B>similar to 20), consistent with scenarios whereby the formation epoch for less massive galaxies is more recent than for massive galaxies.