How homogeneous was the chemical enrichment of the Milky Way 13 gigayears ago?

TL;DR

This study reexamines the early chemical enrichment of the Milky Way halo, finding less scatter in magnesium-to-iron ratios than previously thought, indicating more homogeneous early enrichment than earlier models suggested.

Contribution

It provides a refined analysis using advanced atmospheric models, challenging prior assumptions of inhomogeneous early galaxy enrichment based on observed scatter.

Findings

[Mg/Fe] ratios are narrowly distributed at low metallicities

Early Milky Way halo experienced relatively homogeneous chemical enrichment

Results suggest less stochasticity in early galaxy evolution

Abstract

We reanalyze the chemical composition of the metal-poorest tail of the Galactic halo using highly accurate atmospheric parameters Giribaldi et al. (2021, 2023) and cutting-edge 3D NLTE models Amarsi et al (2018). Most [Mg/Fe] versus [Fe/H] diagrams in the literature exhibit significant scatter at [Fe/H] $\lesssim -2$ dex, often interpreted as evidence of inhomogeneous enrichment during the early phases of galaxy evolution Rossi et al. (2021). However, our analysis of observational data reveals that in the range $-3.5 <$ [Fe/H] $< -2$ dex, the [Mg/Fe] versus [Fe/H] distribution is relatively narrow. This finding suggests a low degree of stochastic enrichment in magnesium during these epochs in the Milky Way halo.