On the chemical evolution of the Milky Way

TL;DR

This paper explores the chemical evolution of the Milky Way through three topics: halo metallicity distribution, age-metallicity relationship, and stellar radial mixing, highlighting analytical derivations, data uncertainties, and simulation results.

Contribution

It provides analytical models for halo metallicity, discusses the impact of data uncertainties on age-metallicity relations, and reviews recent simulations of stellar radial mixing.

Findings

Halo metallicity distribution can be analytically derived.

Age-metallicity relationships are affected by data uncertainties.

Simulations show significant stellar radial mixing in the disk.

Abstract

I discuss three different topics concerning the chemical evolution of the Milky Way (MW). 1) The metallicity distribution of the MW halo; it is shown that this distribution can be analytically derived in the framework of the hierarchical merging scenario for galaxy formation, assuming that the component sub-haloes had chemical properties similar to those of the progenitors of satellite galaxies of the MW. 2) The age-metallicity relationship (AMR) in the solar neighborhood; I argue for caution in deriving from data with important uncertainties (such as the age uncertainties in the Geneva-Kopenhaguen survey) a relationship between average metallicity and age: derived relationships are shown to be systematically flatter than the true ones and should not be directly compared to models. 3) The radial mixing of stars in the disk, which may have important effects on various observables (scatter in AMR, extension of the tails of the metallicity distribution, flatenning of disk abundance profiles). Recent SPH + N-body simulations find considerable radial mixing, but only comparison to observations will ultimately determine the extent of that mixing.