Origin of neutron-capture elements with the Gaia-ESO survey: the evolution of s- and r-process elements across the Milky Way

We investigate the origin of neutron-capture elements by analysing their abundance patterns and radial gradients in the Galactic thin disc. We adopt a detailed two-infall chemical evolution model for the Milky Way, including state-of-the-art nucleosynthesis prescriptions for neutron-capture elements. We consider r-process nucleosynthesis from merging neutron stars (MNS) and magneto-rotational supernovae (MR-SNe), and s-process synthesis from low- and intermediate-mass stars (LIMS) and rotating massive stars. The predictions of our model are compared with data from the sixth data release of the Gaia-ESO survey, from which we consider 62 open clusters with age & GSIM; 0.1 Gyr and & SIM;1300 Milky Way disc field stars. We conclude that: (i) the [Eu/Fe] versus [Fe/H] diagram is reproduced by both prompt and delayed sources, with the prompt source dominating Eu production; (ii) rotation in massive stars significantly contributes to the first peak s-process elements, but MNS and MR-SNe are necessary to match the observations; and (iii) our model slightly underpredicts Mo and Nd, while accurately reproducing the [Pr/Fe] versus [Fe/H] trend. Regarding the radial gradients, we find that: (i) our predicted [Fe/H] gradient slope agrees with observations from Gaia-ESO and other high-resolution spectroscopic surveys; (ii) the predicted [Eu/H] radial gradient slope is steeper than the observed one, regardless of how quick the production of Eu is, prompting discussion on different Galaxy-formation scenarios and stellar radial migration effects; and (iii) elements in the second s-process peak as well as Nd and Pr exhibit a plateau at low-Galactocentric distances, likely due to enhanced enrichment from LIMS in the inner regions.

Automated summary

We investigate the origin of neutron-capture elements in the Galactic thin disc by analysing their abundance patterns and radial gradients. Our detailed two-infall chemical evolution model includes nucleosynthesis prescriptions for neutron-capture elements and considers different synthesis sources. We compare our model predictions with data from the Gaia-ESO survey and find good agreement regarding the [Eu/Fe] versus [Fe/H] diagram and the [Fe/H] gradient slope. However, the predicted [Eu/H] radial gradient slope is steeper than observed, prompting discussion on Galaxy-formation scenarios and stellar radial migration effects. We also note slight underpredictions for Mo and Nd and successful reproduction of the [Pr/Fe] versus [Fe/H] trend.