# The connection between the Galactic halo and ancient Dwarf Satellites

## TL;DR

This study compares chemical abundance patterns of dwarf satellites and Galactic halo stars to assess their connection, highlighting differences in [O/Fe] and [Ba/Fe] ratios and exploring the impact of gas infall on halo formation.

## Contribution

It demonstrates that [Ba/Fe] ratios are more reliable than [O/Fe] for tracing the halo's origins and models the effects of enriched gas infall from dwarf satellites on halo chemical evolution.

## Key findings

- [O/Fe] ratios differ at higher metallicities, indicating limited contribution.
- [Ba/Fe] ratios show consistent discrepancies, suggesting in situ star formation dominates.
- Enriched gas infall influences the chemical composition depending on infall timescale and star formation thresholds.

## Abstract

We explore the hypothesis that the classical and ultra-faint dwarf spheroidal satellites of the Milky Way have been the building blocks of the Galactic halo by comparing their [O/Fe] and [Ba/Fe] versus [Fe/H] patterns with the ones observed in Galactic halo stars. Oxygen abundances deviate substantially from the observed abundances in the Galactic halo stars for [Fe/H] values larger than -2 dex, while they overlap for lower metallicities. On the other hand, for the [Ba/Fe] ratio the discrepancy is extended at all [Fe/H] values, suggesting that the majority of stars in the halo are likely to have been formed in situ. Therefore, we suggest that [Ba/Fe] ratios are a better diagnostic than [O/Fe] ratios. Moreover, we show the effects of an enriched infall of gas with the same chemical abundances as the matter ejected and/or stripped from dwarf satellites of the Milky Way on the chemical evolution of the Galactic halo. We find that the resulting chemical abundances of the halo stars depend on the assumed infall time scale, and the presence of a threshold in the gas for star formation.