The origin of abundance gradients in the Milky Way: the predictions of different models

TL;DR

This study investigates the origin of abundance gradients in the Milky Way's disk, showing that inside-out formation and variable star formation efficiency are key to reproducing observed properties, using a cosmological infall model.

Contribution

It demonstrates that an inside-out disk formation combined with variable star formation efficiency explains the Milky Way's abundance gradients within a cosmological infall framework.

Findings

Inside-out formation is necessary to match abundance and gas density gradients.

A variable star formation efficiency can replicate the effects of a gas density threshold.

Cosmological infall models can reproduce disk properties with appropriate assumptions.

Abstract

We aim at studying the abundance gradients along the Galactic disk and their dependence upon several parameters: a threshold in the surface gas density regulating star formation, the star formation efficiency, the timescale for the formation of the thin disk and the total surface mass density of the stellar halo. We test a model which considers a cosmological infall law. This law does not predict an inside-out disk formation, but it allows to well fit the properties of the solar vicinity. We study several cases. We find that to reproduce at the same time the abundance, star formation rate and surface gas density gradients along the Galactic disk it is necessary to assume an inside-out formation for the disk. The threshold in the gas density is not necessary and the same effect could be reached by assuming a variable star formation efficiency. A cosmologically derived infall law with an inside-out process for the disk formation and a variable star formation efficiency can indeed well reproduce all the properties of the disk. However, the cosmological model presented here does not have sufficient resolution to capture the requested inside-out formation for the disk.