{
  "abstract": "Recent observations combining the power of ALMA and JWST have revealed large ($3-7$ kpc), massive ($3-10\\times10^{10}\\,\\mathrm{M}_\\odot$) stellar bars at $z=4-5$ when the Universe was only 1.2-1.6 Gyr old. At this early epoch, the host galaxy was baryon-dominated (typically 75\\% gas, 25\\% stars) within the observed extent of the disc ($8-15$ kpc). Using NEXUS $N$-body/hydrodynamic simulations, we show that such bars can form promptly (400$-$800 Myr), provided the disc mass fraction is high ($f_{\\rm disc}\\gtrsim 70\\%$) and the bar is gas-dominated at the time of its formation, consistent with the observations. In this limit, gas-free bars are unstable to vertical bending modes, but a dominant gas component suppresses this instability. Unlike massive bars in the local Universe, these early bars were sites of vigorous star formation, as we show. Remarkably, for gas-rich models with $f_{\\rm gas}\\lesssim60\\%$, the bars develop X-shaped boxy bulges; at higher gas fractions ($f_{\\rm gas}> 60\\%$), diffusion suppresses resonant orbit trapping and the emerging bar collapses within 1 Gyr to form a classical bulge. The bar formation time, length, mass, and $m=2$ Fourier amplitude are all inversely related to $f_{\\rm gas}$. We present a simple analytic model for how stochastic forcing shifts the bar onset time, defined as the time at which the growing bar amplitude reaches a specified threshold.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.03275",
  "author_total": 7,
  "authors": [
    {
      "name": "Joss Bland-Hawthorn"
    },
    {
      "name": "Thor Tepper-Garcia"
    },
    {
      "name": "Chris Hamilton"
    },
    {
      "name": "Johan M. Villa-Alatorre"
    },
    {
      "name": "Oscar Agertz"
    },
    {
      "name": "Takafumi Tsukui"
    },
    {
      "name": "Ken Freeman"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/7r3gd5nqh1mp0.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.03275",
  "fulltext_url": null,
  "id": "7r3gd5nqh1mp0",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.03275",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7208736750",
  "pdf_url": "https://arxiv.org/pdf/2609.03275",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-03",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/7r3gd5nqh1mp0.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:31Z",
      "native_id": "2609.03275",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.03275"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Turbulent gas-rich discs at high redshift: the origin of early massive stellar bars",
  "title_text": "Turbulent gas-rich discs at high redshift: the origin of early massive stellar bars",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:31Z",
  "url": "https://research.draconitic.com/paper/7r3gd5nqh1mp0",
  "venue": "arXiv",
  "versions": []
}