The metallicity-luminosity relation at medium redshift based on faint CADIS emission line galaxies

The emission line survey within the Calar Alto Deep Imaging Survey (CADIS) detects galaxies with very low continuum brightness by using an imaging Fabry-Perot interferometer. With spectroscopic follow-up observations Of M-B greater than or similar to -19 CADIS galaxies using FORS2 at the VLT and DOLORES at TNG we obtained oxygen abundances of 5 galaxies at z similar to 0.4 and 10 galaxies at z similar to 0.64. Combining these measurements with published oxygen abundances of galaxies with M-B less than or similar to -19 we find evidence that a metallicity-luminosity relation exists at medium redshift, but it is displaced to lower abundances and higher luminosities compared to the metallicity-luminosity relation in the local universe. Comparing the observed metallicities and luminosities of galaxies at z less than or similar to 3 with Pegase2 chemical evolution models we have found a favoured scenario in which the metallicity of galaxies increases by a factor of similar to2 between z similar to 0.7 and today, and their luminosity decreases by similar to0.5-0.9 mag.