{
  "abstract": "One of the Milky Way’s (MW) characteristic features is a strongly bimodal distribution of α -process elements, such as Mg, at fixed [Fe/H] in stellar abundances. We examine patterns in [Mg/Fe] versus [Fe/H] in FIRE-2 simulations of MW-mass galaxies. Out of 16 galaxies, four are capable of producing a strongly bimodal distribution. In all four galaxies, the high- α population corresponds to an older, radially compact, thick disk, and the low- α population corresponds to a younger, radially extended, thin disk, similar to the MW. The transition from high to low α took 0.3–1.2 Gyr and began 5.5–6.5 Gyr ago. [Mg/Fe] decreased at relatively fixed [Fe/H], both in the galaxy overall and at fixed radii: following a rapid star formation rate (SFR) decline, delayed Fe enrichment from white dwarf supernovae continued, while prompt Mg enrichment from core-collapse supernovae weakened. This transition occurred at a relatively low gas fraction (5%–15%), immediately after the SFR halved within a few hundred Myr. Only one case coincided with a major merger coalescence. We find similar trends in measuring stars by their current radius and by their birth radius; therefore, radial redistribution did not play a dominant role in the formation of a bimodality or its spatial dependence today. Overall, in FIRE-2, strong α -element bimodalities are relatively uncommon (∼25%), are often not associated with a major merger, and arise primarily from a rapid decline in star formation during relatively low gas fraction.",
  "abstract_shown": true,
  "affiliations": [
    "University of California",
    "University of Alabama",
    "LIRA"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Megan Barry",
      "orcid": "0000-0002-1176-0078"
    },
    {
      "affs": [
        0
      ],
      "name": "Andrew Wetzel",
      "orcid": "0000-0003-0603-8942"
    },
    {
      "affs": [
        0
      ],
      "name": "Sarah Loebman",
      "orcid": "0000-0003-3217-5967"
    },
    {
      "affs": [
        1
      ],
      "name": "Jeremy Bailin",
      "orcid": "0000-0001-6380-010X"
    },
    {
      "affs": [
        2
      ],
      "name": "Hanna Parul",
      "orcid": "0009-0007-3431-4269"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/2jbt9ya6h3zsg.bib",
  "cited_by": 0,
  "doi": "10.3847/1538-4357/aea412",
  "fulltext_url": null,
  "id": "2jbt9ya6h3zsg",
  "issns": [
    "0004-637X",
    "1538-4357"
  ],
  "landing_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea412",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7215106310",
  "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea412/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-01",
  "publisher": "American Astronomical Society",
  "ris": "https://research.draconitic.com/paper/2jbt9ya6h3zsg.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:11Z",
      "native_id": "10.3847/1538-4357/aea412",
      "source": "crossref",
      "url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea412"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "openalex:3103|Galaxies: Formation, Evolution, Phenomena",
      "subfield": "galaxies"
    }
  ],
  "title": "The Origin of Strong α -Element Bimodalities in FIRE Simulations of Milky Way–Mass Galaxies",
  "title_text": "The Origin of Strong α -Element Bimodalities in FIRE Simulations of Milky Way–Mass Galaxies",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:11Z",
  "url": "https://research.draconitic.com/paper/2jbt9ya6h3zsg",
  "venue": "The Astrophysical Journal",
  "versions": []
}