The evolution of the mass-metallicity relation up to z≈0.9 from the VIMOS/VLT Deep Survey

We present the first results derived from the spectrophotometric properties of the Vimos VLT Deep Survey (VVDS) first epoch data. We have measured the spectral features (emission/absorption lines, 4000Å break) of a sample a ≈8000 galaxies taken from the VVDS deep 02h and CDFS fields using the platefit VVDS pipeline. We first selected a sub-sample of star-forming galaxies, which were distinguished from narrow-line AGNs by standard and blue diagnostic diagrams. Then the gas-phase oxygen abundances have been derived by fitting all available emission lines towards photo-ionization models. Finally the masses have been derived by fitting all photometric points together with significant spectral features to a library of stellar population models with complex star formation histories. The mass-metallicity relation that we find at low redshifts is in good agreement with previsous studies performed in the local Universe. We find moreover a significant evolution of the mass-metallicity relation with the redshift, the galaxies having on average less metals at a given mass when the redshift increases. We also find a flattening of the mass-metallicity relation up to z ~ 1.