The metallicity of 0.5 < z < 1 field galaxies

We have measured the emission-line ratios in a sample of 34 Canada-France Redshift Survey star-forming galaxies with redshifts in the range of 0.5 < z < 1.0, and we have computed their metallicities by means of the empirically calibrated R-23-metallicity estimator introduced by Pagel et al. The current analysis concentrates on the 15 galaxies with L-H beta > 1.2 x 10(41) ergs s(-1). Although our results can only be regarded as preliminary until near-IR spectroscopy of H alpha and [N II] lambda 6583 are available, the metallicities of these galaxies appear to be remarkably similar to those of local galaxies selected in the same way, and there appears to have been little change in the relationship between metallicity and line and continuum luminosity from z similar to 1 to today. At this stage, our results do not support the idea that these galaxies, known to be generally small and with late-type morphologies, are dwarf galaxies brightened by large bursts of star formation, as had been suggested from previous studies. Rather, our findings are more consistent with a picture in which these systems are the progenitors of today's massive metal-rich galaxies.