Abundance gradients along the Galactic disc from chemical evolution models

V. Grisoni, E. Spitoni, F. Matteucci

Published 2018-05-28Version 1

In this paper, we study the formation and chemical evolution of the Milky Way disc with particular focus on the abundance patterns ([$\alpha$/Fe] vs. [Fe/H]) at different Galactocentric distances, the present-time abundance gradients along the disc and the temporal evolution of abundance gradients. We consider the chemical evolution models for the Galactic disc developed by Grisoni et al. (2017) for the solar neighborhood, both the two-infall and the one-infall, and we extend our analysis to the other Galactocentric distances. In particular, we examine the processes which mainly influence the formation of abundance gradients: i) the inside-out scenario for the formation of the Galactic thin disc, ii) a variable star formation efficiency, and iii) radial gas flows. We compare our model results with recent abundance patterns along the Galactic disc from APOGEE survey and with abundance gradients observed from Cepheids, open clusters, HII regions and PNe. We conclude that the inside-out scenario is a key ingredient, but cannot be the only one to explain abundance patterns at different Galactocentric distances and abundance gradients. Further ingredients, such as radial gas flows and variable star formation efficiency, are needed to reproduce the observed features in the thin disc. In particular, the model with a variable star formation efficiency is in very good agreement with the observational data, both the abundance patterns at different Galactocentric distances and abundance gradients. The model with variable star formation efficiency predicts a flattening of the gradient with time, which is in agreement with other chemical evolution models and cosmological simulations, but it does not allow the inversion of gradients, observed at high redshift.