2020/05/31 by Sebastian Trujillo-Gomez, J. M. Diederik Kruijssen, Marta Reina-Campos +5 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.1093/mnras/stab341
published as Monthly Notices of the Royal Astronomical Society, Volume 503, Issue 1, pp.31-58, May 2021 · 24 pages, 20 figures. Published in MNRAS
arxiv created 2021/03/30 · arxiv updated 2021/03/31
We present a detailed comparison of the Milky Way (MW) globular cluster (GC) kinematics with the 25 Milky Way-mass cosmological simulations from the E-MOSAICS project. While the MW falls within the kinematic distribution of GCs spanned by the simulations, the relative kinematics of its metal-rich ([\rmFe/H]>-1.2) versus metal-poor ([\rmFe/H]<-1.2), and inner (r<8\rmkpc) versus outer (r>8\rmkpc) populations are atypical for its mass. To understand the origins of these features, we perform a comprehensive statistical analysis of the simulations, and find 18 correlations describing the assembly of L^* galaxies and their dark matter haloes based on their GC population kinematics. The correlations arise because the orbital distributions of accreted and in-situ GCs depend on the masses and accretion redshifts of accreted satellites, driven by the combined effects of dynamical fraction, tidal stripping, and dynamical heating. Because the kinematics of in-situ/accreted GCs are broadly traced by the metal-rich/metal-poor and inner/outer populations, the observed GC kinematics are a sensitive probe of galaxy assembly. We predict that relative to the population of L^* galaxies, the MW assembled its dark matter and stellar mass rapidly through a combination of in-situ star formation, more than a dozen low-mass mergers, and 1.4±1.2 early (z=3.1±1.3) major merger. The rapid assembly period ended early, limiting the fraction of accreted stars. We conclude by providing detailed quantitative predictions for the assembly history of the MW.