The Galaxy and its stellar halo - insights from a hybrid cosmological approach

TL;DR

This study combines high-resolution N-body simulations with semi-analytic models to explore the formation and properties of the Milky Way's stellar halo, revealing its origin from a few massive early accreted satellites.

Contribution

It introduces a hybrid cosmological approach to model the Milky Way and its stellar halo, aligning simulated properties with observations and elucidating halo formation mechanisms.

Findings

Stellar halo mainly formed from a few massive early satellites.

No metallicity gradient observed in the halo.

Higher metallicity stars are more centrally concentrated.

Abstract

We use a series of high-resolution N-body simulations of a `Milky-Way' halo, coupled to semi-analytic techniques, to study the formation of our own Galaxy and of its stellar halo. Our model Milky Way galaxy is a relatively young system whose physical properties are in quite good agreement with observational determinations. In our model, the stellar halo is mainly formed from a few massive satellites accreted early on during the galaxy's lifetime. The stars in the halo do not exhibit any metallicity gradient, but higher metallicity stars are more centrally concentrated than stars with lower abundances. This is due to the fact that the most massive satellites contributing to the stellar halo are also more metal rich, and dynamical friction drags them closer to the inner regions of the host halo.