Simulations Reveal Why Disc-Origin Globular Clusters Fail as Reliable Merger Tracers, Refining Gaia-Sausage-Enceladus Chronology

This arXiv preprint (not yet peer-reviewed) deploys three N-body simulations of the Milky Way–Gaia-Sausage-Enceladus (GSE) merger, varying progenitor mass, mass ratio, and gas fraction, to track globular cluster (GC) orbits in E-Lz space. Unlike earlier observational mappings that placed most metal-poor GCs with GSE debris, the models demonstrate that disc-born GCs lose substantial orbital energy through repeated disc passages and tidal shocks, often falling below the energy envelope of GSE stars even 9 Gyr post-merger; halo GCs and in-situ merger-formed clusters retain their kinematic imprint. The work thereby validates prior age-metallicity plus E-Lz associations for the surviving halo population while explaining the apparent scarcity of disc GCs linked to GSE. Limitations include idealized initial conditions that omit full cosmological context and live stellar feedback, plus reliance on only three realizations rather than a statistical ensemble. Cross-referenced with Belokurov et al. (2018, MNRAS, Gaia Sausage discovery) and Helmi et al. (2018, Nature, kinematic decomposition), the findings imply that large-scale Milky Way assembly maps derived solely from present-day GC kinematics systematically undercount early massive mergers unless halo subsets are prioritized.