{
  "abstract": "We study the build-up and survival of angular momentum in the stellar disc using a statistical suite of cosmological simulations of Milky Way-mass galaxies. Our results show that stellar kinematics at $z=0$ rarely recover the true times of disc spin-up, due to the disruptive impact of massive radial merger events. The proto-disc (i.e. Aurora) and kicked-up disc stars (the Splash) become indistinguishable at low metallicities, and the local fraction of kicked-up disc stars remains $< 20$ per cent even after major mergers. In contrast, observations from Gaia and legacy surveys reveal that Galactic $\\alpha$-rich populations as old as $\\tau =13.5\\, \\rm {Gyr}$ show significant rotation, with median $\\eta > 0.75$. This places strong constraints on the total merger ratio between the proto-Milky Way and its last significant merger (Gaia-Sausage-Enceladus, GSE), favouring minor mergers with mass ratios $< 1:4$. We present the age–metallicity relation for the stellar halo and estimate the interaction epoch at $\\tau _{\\rm {spin\\text{-}up}}\\simeq \\tau _{\\rm {GSE}}\\sim 11\\, \\rm {Gyr}$. We note an abrupt dearth of halo and Splash stars after a lookback time of $10\\, \\rm {Gyr}$, marking the end of the merger interaction. Finally, we show that Globular Clusters in the metallicity range $-0.8<\\rm {[Fe/H]}< -0.3$ share a formation time of $\\tau _{\\rm {starburst}}\\sim 11\\, \\rm {Gyr}$, which we interpret as a signature of a starburst triggered by the first pericentric interaction of the GSE. This is remarkable corroboration between our GSE interaction and starburst times of $\\tau _{\\rm GSE}=\\tau _{\\rm starburst} \\sim 11\\,$ Gyr.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2509.09576",
  "author_total": 2,
  "authors": [
    {
      "name": "Matthew Orkney"
    },
    {
      "name": "Chervin Laporte"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/0yehv4zzsqkj9.bib",
  "cited_by": 10,
  "doi": "10.1093/mnras/staf2154",
  "fulltext_url": null,
  "id": "0yehv4zzsqkj9",
  "issns": [
    "0035-8711",
    "1365-2966"
  ],
  "landing_url": "https://hal.science/hal-05855816v1",
  "language": "en",
  "licence": "CC-BY",
  "licence_label": "CC BY",
  "licence_source": "journal",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "hal",
      "0.phys"
    ],
    [
      "hal",
      "1.phys.astr"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7160529478",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-06-05",
  "publisher": "Oxford University Press (OUP): Policy P - Oxford Open Option A",
  "ris": "https://research.draconitic.com/paper/0yehv4zzsqkj9.ris",
  "sources": [
    {
      "first_seen": "2026-11-07T12:20:26Z",
      "native_id": "hal-05855816",
      "source": "hal",
      "url": "https://hal.science/hal-05855816v1"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "openalex:3103|Galaxies: Formation, Evolution, Phenomena",
      "subfield": "galaxies"
    }
  ],
  "title": "Build-up and survival of the disc: from numerical models of galaxy formation to the Milky Way",
  "title_text": "Build-up and survival of the disc: from numerical models of galaxy formation to the Milky Way",
  "type": "peer-reviewed",
  "updated_at": "2026-11-09T12:20:29Z",
  "url": "https://research.draconitic.com/paper/0yehv4zzsqkj9",
  "venue": "Monthly Notices of the Royal Astronomical Society",
  "versions": []
}