${S}^5$: The destruction of a bright dwarf galaxy as revealed by the chemistry of the Indus stellar stream

TL;DR

The paper reveals the complex chemical signatures of the Indus stellar stream, providing evidence of a disrupted dwarf galaxy with a globular cluster and highlighting stars with extreme r-process element enhancements.

Contribution

It presents the first detailed chemical analysis of the Indus stream, identifying diverse stellar signatures and evidence of a disrupted dwarf galaxy with a globular cluster.

Findings

Indus_13 shows extreme r-process enhancement with [Eu/Fe] = +1.81.

Indus_0 exhibits globular cluster-like chemical signatures.

The progenitor was likely a chemically evolved dwarf galaxy.

Abstract

The recently discovered Indus stellar stream exhibits a diverse chemical signature compared to what is found for most other streams due to the abundances of two outlier stars, Indus$\_$0 and Indus$\_$13. Indus$\_$13, exhibits an extreme enhancement in rapid neutron-capture ($r$-)process elements with $\mathrm{[Eu/Fe]} = +1.81$. It thus provides direct evidence of the accreted nature of $r$-process enhanced stars. In this paper we present a detailed chemical analysis of the neutron-capture elements in Indus$\_$13, revealing the star to be slightly actinide poor. The other outlier, Indus$\_0$, displays a globular cluster-like signature with high N, Na, and Al abundances, while the rest of the Indus stars show abundances compatible with a dwarf galaxy origin. Hence, Indus$\_0$ provides the first chemical evidence of a fully disrupted dwarf containing a globular cluster. We use the chemical signature of the Indus stars to discuss the nature of the stream progenitor which was likely a chemically evolved system, with a mass somewhere in the range from Ursa Minor to Fornax.