Chemical enrichment in very low-metallicity environments: Bootes I

TL;DR

This study models the chemical evolution of the ultrafaint dwarf galaxy Bootes I, comparing classical and cosmologically-motivated scenarios, and examines the role of gas mixing and external stripping processes in its evolution.

Contribution

It introduces cosmologically-motivated accretion models and assesses the impact of inhomogeneous mixing, providing new insights into Bootes I's star formation and gas loss mechanisms.

Findings

Bootes I formed stars with very low efficiency.

No clear evidence of long-lasting supernova-driven outflows.

External stripping mechanisms likely explain the lack of neutral gas.

Abstract

We present different chemical evolution models for the ultrafaint dwarf galaxy Bootes I. We either assume that the galaxy accretes its mass through smooth infall of gas of primordial chemical composition (classical models) or adopt mass accretion histories derived from the combination of merger trees with semi-analytical modelling (cosmologically-motivated models). Furthermore, we consider models with and without taking into account inhomogeneous mixing in the ISM within the galaxy. The theoretical predictions are then compared to each other and to the body of the available data. From this analysis, we confirm previous findings that Bootes I has formed stars with very low efficiency but, at variance with previous studies, we do not find a clear-cut indication that supernova explosions have sustained long-lasting galactic-scale outflows in this galaxy. Therefore, we suggest that external mechanisms such as ram pressure stripping and tidal stripping are needed to explain the absence of neutral gas in Bootes I today.