Probing the relation between UV slope and stellar metallicity at z > 2

The measurement of the stellar metallicity in galaxies is fundamental to understand their evolution across cosmic epochs, but is very difficult as it requires high signal-to-noise spectra. Benefiting from uniquely deep, UV rest-frame spectra of 600 star-forming galaxies at redshifts between 2 and 5.5 from the VANDELS survey, I derive the stellar metallicity from two absorption features at 1501 and 1719 Angstrom, which are metal sensitive features produced in the photosphere of young O-B stars. I will show for this sample the mass-metallicity relation, and a relation between the stellar metallicity and the UV-continuum slope (a proxy for the dust attenuation). The latter sheds light on the joint evolution of metal and dust content in galaxies between 2 and 3 Gyr after the Big Bang, and will allow the characterization of large statistical samples of galaxies at even earlier epochs with next generation telescopes