Evidence of Gaia Enceladus experiencing at least two passages around the Milky Way
\'Asa Sk\'ulad\'ottir, Heitor Ernandes, Diane K. Feuillet, Alice Mori, Sofia Feltzing, Romain E. R. Lucchesi, Paola Di Matteo

TL;DR
This paper provides observational evidence that the Gaia Enceladus galaxy experienced multiple passages through the Milky Way, revealing details about its structure and merger history through chemical and kinematic analysis.
Contribution
It is the first to confirm multiple passages of Gaia Enceladus using high-precision chemical and kinematic data, including new aluminum measurements.
Findings
Evidence of two distinct stellar populations from Gaia Enceladus
Stars with high energy originate from outer regions, low energy from inner regions
Gaia Enceladus experienced several passages before merging
Abstract
One of the major recent breakthroughs has been the discovery of the last Major Merger to happen in the history of the Milky Way. Around 10 Gyr ago the galaxy Gaia Enceladus, with estimated ~10% of the Milky Way mass, fell into its potential, bringing a large amount of stars which can be identified through their unique chemical and kinematic signatures. Simulations have long predicted that a galaxy of this size should experience several passages through the disk of the Milky Way before eventually being fully dispersed. For the first time, we present observational evidence to support this. We identify two subpopulations accreted from Gaia Enceladus: 1) stars which today have large kinematic energy, which originate from the outskirts of Gaia Enceladus and were accreted during early passages; 2) stars with low kinetic energy accreted at later passages, originating from the inner parts of…
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