The Gaia-ESO Survey: radial distribution of abundances in the Galactic
  disc from open clusters and young field stars
  The spatial distribution of elemental abundances in the disc of our Galaxy
gives insights both on its assembly process and subsequent evolution, and on
the stellar nucleogenesis of the different elements. Gradients can be traced
using several types of objects as, for instance, (young and old) stars, open
clusters, HII regions, planetary nebulae. We aim at tracing the radial
distributions of abundances of elements produced through different
nucleosynthetic channels -the alpha-elements O, Mg, Si, Ca and Ti, and the
iron-peak elements Fe, Cr, Ni and Sc - by using the Gaia-ESO idr4 results of
open clusters and young field stars. From the UVES spectra of member stars, we
determine the average composition of clusters with ages >0.1 Gyr. We derive
statistical ages and distances of field stars. We trace the abundance gradients
using the cluster and field populations and we compare them with a
chemo-dynamical Galactic evolutionary model. Results. The adopted
chemo-dynamical model, with the new generation of metallicity-dependent stellar
yields for massive stars, is able to reproduce the observed spatial
distributions of abundance ratios, in particular the abundance ratios of [O/Fe]
and [Mg/Fe] in the inner disc (5 kpc<RGC <7 kpc), with their differences, that
were usually poorly explained by chemical evolution models. Often, oxygen and
magnesium are considered as equivalent in tracing alpha-element abundances and
in deducing, e.g., the formation time-scales of different Galactic stellar
populations. In addition, often [alpha/Fe] is computed combining several
alpha-elements. Our results indicate, as expected, a complex and diverse
nucleosynthesis of the various alpha-elements, in particular in the high
metallicity regimes, pointing towards a different origin of these elements and
highlighting the risk of considering them as a single class with common
features.
