The KLEVER Survey: metallicity maps and gradients

We present near-infrared observations of 42 gravitationally lensed galaxies obtained in the framework of the KMOS Lensed Emission Lines and VElocity Review (KLEVER) Survey, a programme aimed at investigating the spatially resolved properties of the ionized gas in 1.2<z<2.5 galaxies by means of a full coverage of the YJ, H, and K near-infrared bands. Detailed metallicity maps and gradients are derived for a subsample of 28 galaxies from reconstructed source-plane emission-line maps, exploiting the variety of different emission-line diagnostics provided by the broad wavelength coverage of the survey.

About 85 per cent of these galaxies are characterized by metallicity gradients shallower than 0.05dex/kpc and 89 per cent are consistent with a flat slope within 3{sigma} (67 per cent within 1{sigma}), suggesting a mild evolution with cosmic time. In the context of cosmological simulations and chemical evolution models, the presence of efficient feedback mechanisms and/or extended star formation profiles on top of the classical 'inside-out' scenario of mass assembly is generally required to reproduce the observed flatness of the metallicity gradients beyond z~1.