Resolving local and global kinematic signatures of satellite mergers with billion particle simulations

In this work, we present two new ∼109 particle self-consistent simulations of the merger of a Sagittarius-like dwarf galaxy with a Milky Way (MW)-like disc galaxy. One model is a violent merger creating a thick disc, and a Gaia-Enceladus/Sausage-like remnant. The other is a highly stable disc which we use to illustrate how the improved phase space resolution allows us to better examine the formation and evolution of structures that have been observed in small, local volumes in the MW, such as the z-vz phase spiral and clustering in the vR-vφ plane when compared to previous works. The local z-vz phase spirals are clearly linked to the global asymmetry across the disc: we find both 2-armed and 1-armed phase spirals, which are related to breathing and bending behaviours, respectively. Hercules-like moving groups are common, clustered in vR-vφ in local data samples in the simulation. These groups migrate outwards from the inner galaxy, matching observed metallicity trends even in the absence of a galactic bar. We currently release the best-fitting 'present-day' merger snapshots along with the unperturbed galaxies for comparison.JASH is supported by a Flatiron Research Fellowship at the Flatiron institute, which is supported by the Simons Foundation. KVJ was supported by National Science Foundation (NSF) grant AST-1715582. CFPL acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 852839). This work was supported in part by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan