Gastro Library. I. The Simulated Chemodynamical Properties of Several Gaia–Sausage–Enceladus-like Stellar Halos

The Milky Way stellar halo contains relics of ancient mergers that tell the story our Galaxy's formation. Some them are identified due to their similarity in energy, actions and chemistry, referred as "chemodynamical space", often attributed distinct merger events. It is also known Galaxy went through a significant event shaped local during its first Gyr. Previous studies using $N$-body only cosmological hydrodynamical simulations have shown such single massive can produce several "signatures" chemodynamical space, which potentially be misinterpreted Motivated by these, this work we use subset GASTRO, library consists SPH+$N$-body models accretion Way-like galaxy. Here, study with orbital properties similar main explore implications substructures. We find that: $i.$ supernova feedback efficiency influences satellite's structure evolution, resulting features for same initial conditions, $ii.$ very retrograde high energy stars most metal-poor accreted dwarf galaxy could $iii.$ bound more metal-rich models, opposite what observed Way, suggesting secondary merger, finally $iv.$ reconcile other substructures an unique progenitor.