Cosmological insights into the early accretion of r-process-enhanced stars II. Dynamical identification of lost members of Reticulum II

TL;DR

This study uses dynamical modeling and chemical analysis to identify former members of the Reticulum II galaxy among r-process-enhanced stars, revealing at least 93 stars likely originated from it.

Contribution

It introduces a detailed N-body dynamical model to trace the origins of r-process-enhanced stars and identify their connection to Reticulum II.

Findings

At least 93 of 530 r-process-enhanced stars are former Reticulum II members.

Dynamical phase-space analysis links stars to the galaxy's tidal tails.

The modeling confirms the progenitor association of several peculiar stars.

Abstract

Aims. We identify the possible dynamical connection between individual r-process-enhanced stars and the ultra-faint dwarf galaxy Reticulum II based on the current phase-space information for these stars and the dynamical mass-loss model of Reticulum II during its orbital motion for 11.5 Gyr of lookback time. The dynamical orbital modelling together with the chemical abundance analysis proved to be useful tools for the progenitor identification of the peculiar stars in our Galaxy. Methods. To reproduce the Reticulum II orbital mass loss, we used our high-precision N-body phi-GPU code to integrate almost 1 million stars into the system evolution inside a external Galactic potential. We also investigated the orbits of r-process-enhanced stars using the same code. Results. We present our Reticulum II dynamical modelling results in the context of the stars energies - angular momentum phase-space and phase-space overlapping of the currently observed r-process-enhanced stars with Reticulum II stellar tidal tails. Of the 530 r-stars known today, at least 93 are former members of the Reticulum II dynamical progenitor system.