The Metallicity of 0 . 5 < z < 1

We are undertaking a program to measure emission line ratios in a selected sample of 0.5 < z < 1.0 CFRS starforming galaxies in order to compute their Interstellar Medium metallicities. The latter are derived by means of the empirically-calibrated R23 estimator introduced by Pagel et al. (1979). Here we focus on a subsample of 15 galaxies with LHβ > 1.2 × 10 41 erg s. In addition to the optical CFHT spectra discussed in Carollo & Lilly (2001), where a preliminary account of this work can be found, in this paper we also refer to new J-band Keck spectroscopy of the Hα and [NII]6583 lines for several objects. These lines allow us to break the degeneracy between low (< ∼ 0.1Z⊙) and high (>∼ 0.5Z⊙) metallicity of the R23 estimator, and put on solid ground the finding that the 0.5 < z < 1.0 blue galaxies in the high-LHβ sample are significantly metal-enriched (Z > ∼ 0.3Z⊙ up to Z⊙). Therefore, our results do not support previous suggestions in which the 0.5 < z < 1.0 starforming galaxies are dwarf galaxies brightened by large bursts of star-formation, but support instead a picture where at least a significant fraction of them evolves to become today’s massive metal-rich systems.