{
  "abstract": "We present a post-processing pipeline that predicts CO line luminosities, molecular hydrogen masses, and CO abundances for galaxies in the Feedback in Realistic Environments (FIRE-2) simulations, as a first step toward CO response functions for line intensity mapping mocks. SKIRT gives the radiation field reaching each gas cell. CLOUDY, tabulated on a five-parameter grid (metallicity, density, turbulent velocity, radiation field, cloud scale) and interpolated, gives $L'_{\\rm CO(1-0)}$ and the $\\rm H_2$ and CO masses. In this first of three papers we validate the pipeline against observations. For Milky Way (MW) molecular clouds, the predicted $L'_{\\rm CO(1-0)}$ rises sharply at $A_V\\sim1$ and matches the observed values above that column. For a uniform $3\\,Z_\\odot$ the summed luminosity is within 35\\% of the observed total. A factor of three increase in metallicity changes the total $L'_{\\rm CO(1-0)}$ by an order of magnitude. Along MW sight lines, the predicted $N_{\\rm CO}/N_{\\rm H_2}$ reproduces the observed upturn within 0.3 dex in $N_{\\rm H_2}$ but falls below the data at higher columns. At $z=0$ our molecular gas masses agree with xCOLD GASS for ${\\rm SFR}\\gtrsim0.3\\,M_\\odot\\,yr^{-1}$ and are converged across our simulation resolutions. At $z\\gtrsim1$ observed gas masses exceed ours at fixed stellar mass, though selection effects and conversion-factor assumptions limit this comparison. CO luminosities are compared with extragalactic observations in Paper II. Capturing the metallicity-dependent dust shielding of CO from photodissociation is essential for modeling CO emission in low-mass and high-redshift galaxies.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.12159",
  "author_total": 8,
  "authors": [
    {
      "name": "Doğa Tolgay"
    },
    {
      "name": "Norman W. Murray"
    },
    {
      "name": "Dongwoo Chung"
    },
    {
      "name": "J. Richard Bond"
    },
    {
      "name": "Nathan J. Carlson"
    },
    {
      "name": "Robert Feldmann"
    },
    {
      "name": "Andrew Wetzel"
    },
    {
      "name": "Guochao Sun"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/dadvxfspzp4q6.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.12159",
  "fulltext_url": null,
  "id": "dadvxfspzp4q6",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.12159",
  "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.CO"
    ],
    [
      "arxiv",
      "astro-ph.GA"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7221086448",
  "pdf_url": "https://arxiv.org/pdf/2610.12159",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-08",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/dadvxfspzp4q6.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:54Z",
      "native_id": "2610.12159",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.12159"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Modeling CO Line Luminosity Using FIRE Simulations: I. Methodology and Validation of Molecular Gas and CO Abundance",
  "title_text": "Modeling CO Line Luminosity Using FIRE Simulations: I. Methodology and Validation of Molecular Gas and CO Abundance",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:54Z",
  "url": "https://research.draconitic.com/paper/dadvxfspzp4q6",
  "venue": "arXiv",
  "versions": []
}