Understanding the Impact of Formation History on the Dynamical Distribution of Substructure using the Milky Way-est Simulation Suite

Recent efforts to understand the dynamical history of the Milky Way by exploring the observational signatures of accreted substructure have yielded a number of interesting results. However, it is difficult to interpret the significance of the results in a cosmological context because the unique formation history of the Milky Way can lead to a distribution of substructure which significantly diverges from a typical galaxy of its mass. Here, we attempt to contextualize the impact of the Milky Way’s accretion history using the first suite of cosmological zoom-in simulations constrained to resemble the accretion history of the Milky Way (Buch et al., in prep). The suite consists of 25 Milky Way mass host halos (1.0–1.8 × 10¹² M_☉) all of which were chosen to have an identified GE and LMC analog. We use detailed particle tracking to trace individual halos down to the simulation resolution limit (~10⁸ M_☉). This allows us to explore in detail the effect these recent mergers have on the anisotropy of the Milky Way’s dark matter halo. In addition, combining particle tagging methods with stellar mass estimates from UniverseMachine allows us to study the effects of merger history on phase-space clustering of disrupted substructure. These results can help to understand the robustness and biases of observational studies of phase-space clustering in the stellar halo.