Cosmological insights into the early accretion of r-process-enhanced stars

II. Dynamical identification of lost members of Reticulum II

¹ Main Astronomical Observatory, National Academy of Sciences of Ukraine, 27 Akademika Zabolotnoho St, 03143 Kyiv, Ukraine
² Nicolaus Copernicus Astronomical Centre Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
³ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, HUN-REN CSFK, MTA Centre of Excellence, Konkoly Thege Miklós út 15–17, 1121 Budapest, Hungary
⁴ Department of Physics, Zarqa University, Zarqa 13110, Jordan
⁵ Jordanian Astronomical Virtual Observatory, Zarqa University, Zarqa 13110, Jordan

^★ Corresponding author; berczik@mao.kiev.ua

Received: 8 August 2024
Accepted: 4 November 2024

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 φ–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.