Chemical abundances as population tracers

TL;DR

This paper discusses how elemental abundance ratios in stars serve as tracers for understanding the Galaxy's chemical evolution, highlighting the importance of 3D non-LTE corrections and differential analysis across different stellar populations.

Contribution

It emphasizes the significance of 3D non-LTE corrections and differential methods in accurately tracing stellar populations and Galactic chemical evolution.

Findings

3D non-LTE corrections significantly affect abundance ratio trends.

Differential analysis reveals multiple discrete populations in Galactic components.

Abundance ratios like C/O, Na/Fe, and alpha/Fe indicate diverse stellar populations.

Abstract

Elemental abundance ratios as tracers of stellar populations are discussed with emphasis on F, G, and K stars providing a `fossil' record of the chemical evolution of the Galaxy. Most abundance studies have been based on homogeneous 1D model atmospheres and the assumption of local thermodynamic equilibrium (LTE), but recent works have shown that 3D non-LTE corrections can change the derived trends of abundance ratios as a function of stellar metallicity very significantly. However, when comparing stars having similar effective temperatures, surface gravities, and metallicities, 3D non-LTE corrections tend to cancel out. When applying such a differential approach to stars in the Galactic disk, bulge, and halo, abundance ratios like C/O, Na/Fe, alpha/Fe, Cu/Fe, Ba/Y, and Eu/Ba point to the existence of multiple discrete populations in each of these Galactic components.