{
  "abstract": "We present very deep (≈11 hours on-source) JWST/MIRI low-resolution spectroscopy of the rest-frame optical emission of U37126, a UV-bright ( M UV ≃ −20) mildly lensed ( μ ≃ 2.2) galaxy at z = 10.255. The continuum emission is well detected in the NIRSpec and MIRI spectra, but no nebular recombination or metal emission lines are observed ( EW 0 (H β +[O III ]) ≤ 300 Å and EW 0 (H α ) ≤ 400 Å at 3 σ ). Combined with the exceptionally blue UV continuum slope, β UV ≃ −2.9, and flat Balmer break, these constraints indicate a stellar population dominated by very young and massive stars with a strongly suppressed nebular contribution. Comparisons with synthetic stellar population models indicate that U37126 requires a very high ionizing photon production efficiency, log( ξ ion /Hz erg −1 ) ≃ 25.75, and a nearly unity Lyman continuum escape fraction, of f esc ≥ 86% (3 σ ) based on the H α flux limit and f esc = 0.94 ± 0.06 derived independently from fitting the spectral energy distribution (SED). The best-fit SED yields a (delensed) stellar mass of M ★ ≃ 10 7.8 M ⊙ and a star formation rate SFR ≃ 10 M ⊙ yr −1 (specific SFR ∼ 160 Gyr −1 ). Together with its very compact size, r eff ≃ 61 pc, this yields a very high stellar mass and SFR surface densities, Σ M ★ ≃ 3 × 10 3 M ⊙ pc −2 and Σ SFR ≃ 400 M ⊙ yr −1 kpc −2 . Together with the lack of detectable nebular emission, these properties suggest that U37126 is undergoing a so-called interstellar medium-naked starburst phase, possibly driven by an extremely efficient gas-to-star conversion followed by strong feedback that has cleared the remaining gas from its stellar core, which allowed most Lyman continuum photons to escape. Finally, we show that even a small fraction of galaxies such as U37126 (≃3–6%), with an extreme Lyman continuum production and escape, might contribute disproportionately (≃50–100%) to the ionizing photon budget during cosmic reionization.",
  "abstract_shown": true,
  "affiliations": [
    "Geneva Observatory, Department of Astronomy, University of Geneva",
    "Centro de Astrobiología (CAB), CSIC-INTA",
    "European Space Agency (ESA), ESA Office, Space Telescope Science Institute",
    "Department of Astronomy, Indiana University",
    "Departamento de Física de la Tierra y Astrofísica, Facultad de Ciencias Físicas, Universidad Complutense de Madrid",
    "Leiden Observatory, Leiden University",
    "INAF – Osservatorio Astronomico di Roma",
    "Kapteyn Astronomical Institute, University of Groningen",
    "Space Telescope Science Institute (STScI)",
    "Center for Frontier Science, Chiba University",
    "David A. Dunlap Department of Astronomy and Astrophysics, University of Toronto",
    "Dunlap Institute for Astronomy and Astrophysics",
    "Institute for Cosmic Ray Research, The University of Tokyo",
    "Division of Physics, Faculty of Pure and Applied Sciences, University of Tsukuba",
    "Tomonaga Center for the History of the Universe (TCHoU), Faculty of Pure and Applied Sciences, University of Tsukuba",
    "Department of Astronomy, University of Texas",
    "Institute of Science and Technology Austria (ISTA)",
    "Department of Physics, School of Advanced Science and Engineering, Faculty of Science and Engineering, Waseda University",
    "Waseda Research Institute for Science and Engineering, Faculty of Science and Engineering, Waseda University",
    "DARK, Niels Bohr Institute, University of Copenhagen",
    "University of Massachusetts Amherst",
    "Department of Astronomy, Stockholm University, Oscar Klein Centre, AlbaNova University Centre",
    "AURA for the European Space Agency (ESA), Space Telescope Science Institute",
    "UK Astronomy Technology Centre, Royal Observatory Edinburgh"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 34,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "R. Marques-Chaves",
      "orcid": "0000-0001-8442-1846"
    },
    {
      "affs": [
        1
      ],
      "name": "Javier Álvarez-Márquez",
      "orcid": "0000-0002-7093-1877"
    },
    {
      "affs": [
        1
      ],
      "name": "Luis Colina",
      "orcid": "0000-0002-9090-4227"
    },
    {
      "affs": [
        2
      ],
      "name": "Sarah Kendrew",
      "orcid": "0000-0002-7612-0469"
    },
    {
      "affs": [
        3
      ],
      "name": "Abdurro'uf",
      "orcid": "0000-0002-5258-8761"
    },
    {
      "affs": [
        1,
        4
      ],
      "name": "Carmen Blanco-Prieto",
      "orcid": "0009-0005-5448-5239"
    },
    {
      "affs": [
        5
      ],
      "name": "Leindert Boogaard",
      "orcid": "0000-0002-3952-8588"
    },
    {
      "affs": [
        6
      ],
      "name": "M. Castellano",
      "orcid": "0000-0001-9875-8263"
    },
    {
      "affs": [
        7
      ],
      "name": "K. I. Caputi",
      "orcid": "0000-0001-8183-1460"
    },
    {
      "affs": [
        8
      ],
      "name": "Alejandro Crespo Gómez",
      "orcid": "0000-0003-2119-277X"
    },
    {
      "affs": [
        6
      ],
      "name": "A. Fontana",
      "orcid": "0000-0003-3820-2823"
    },
    {
      "affs": [
        9
      ],
      "name": "Yoshinobu Fudamoto",
      "orcid": "0000-0001-7440-8832"
    },
    {
      "affs": [
        10,
        11
      ],
      "name": "S. Fujimoto",
      "orcid": "0000-0001-7201-5066"
    },
    {
      "affs": [
        2
      ],
      "name": "M. García-Marín",
      "orcid": "0000-0003-4801-0489"
    },
    {
      "affs": [
        12
      ],
      "name": "Yuichi Harikane",
      "orcid": "0000-0002-6047-430X"
    },
    {
      "affs": [
        8
      ],
      "name": "Santosh Harish",
      "orcid": "0000-0003-0129-2079"
    },
    {
      "affs": [
        13,
        14
      ],
      "name": "Takuya Hashimoto",
      "orcid": "0000-0002-0898-4038"
    },
    {
      "affs": [
        15
      ],
      "name": "T. Hsiao"
    },
    {
      "affs": [
        16
      ],
      "name": "Edoardo Iani",
      "orcid": "0000-0001-8386-3546"
    },
    {
      "affs": [
        17,
        18
      ],
      "name": "Akio K. Inoue",
      "orcid": "0000-0002-7779-8677"
    },
    {
      "affs": [
        19
      ],
      "name": "Danial Langeroodi",
      "orcid": "0000-0001-5710-8395"
    },
    {
      "affs": [
        20
      ],
      "name": "R. Lin"
    },
    {
      "affs": [
        21
      ],
      "name": "Jens Melinder",
      "orcid": "0000-0003-0470-8754"
    },
    {
      "affs": [
        6
      ],
      "name": "Lorenzo Napolitano",
      "orcid": "0000-0002-8951-4408"
    },
    {
      "affs": [
        21
      ],
      "name": "Göran Östlin",
      "orcid": "0000-0002-3005-1349"
    },
    {
      "affs": [
        1
      ],
      "name": "Pablo G. Pérez‐González",
      "orcid": "0000-0003-4528-5639"
    },
    {
      "affs": [
        1,
        4
      ],
      "name": "Carlota Prieto-Jiménez",
      "orcid": "0009-0005-4109-161X"
    },
    {
      "affs": [
        22
      ],
      "name": "P. Rinaldi",
      "orcid": "0000-0002-5104-8245"
    },
    {
      "affs": [
        1
      ],
      "name": "Bruno Rodríguez Del Pino",
      "orcid": "0000-0001-5171-3930"
    },
    {
      "affs": [
        6
      ],
      "name": "Paola Santini",
      "orcid": "0000-0002-9334-8705"
    },
    {
      "affs": [
        17,
        18
      ],
      "name": "Yuma Sugahara",
      "orcid": "0000-0001-6958-7856"
    },
    {
      "affs": [
        1,
        4
      ],
      "name": "A. Varo-O'ferral",
      "orcid": "0009-0005-7278-1541"
    },
    {
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        23
      ],
      "name": "G. S. Wright",
      "orcid": "0000-0001-7416-7936"
    },
    {
      "affs": [
        20
      ],
      "name": "J. Zavala"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/f8kk5n8kd8gej.bib",
  "cited_by": 21,
  "doi": "10.1051/0004-6361/202659281",
  "fulltext_url": null,
  "id": "f8kk5n8kd8gej",
  "issns": [
    "0004-6361",
    "1432-0746"
  ],
  "landing_url": "https://doi.org/10.1051/0004-6361/202659281",
  "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": [
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
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  "openalex": "W7165645822",
  "pdf_url": null,
  "pmcid": null,
  "pmid": null,
  "published": "2026-06-23",
  "publisher": "EDP Sciences",
  "ris": "https://research.draconitic.com/paper/f8kk5n8kd8gej.ris",
  "sources": [
    {
      "first_seen": "2026-11-08T13:20:39Z",
      "native_id": "W7165645822",
      "source": "openalex",
      "url": "https://doi.org/10.1051/0004-6361/202659281"
    }
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  "subjects": [
    {
      "field": "astronomy",
      "origin": "openalex:3103|Galaxies: Formation, Evolution, Phenomena",
      "subfield": "galaxies"
    }
  ],
  "title": "PRISMS: U37126, a very blue ISM-naked starburst at z = 10.255 with a nearly 100% Lyman continuum escape fraction",
  "title_text": "PRISMS: U37126, a very blue ISM-naked starburst at z = 10.255 with a nearly 100% Lyman continuum escape fraction",
  "type": "peer-reviewed",
  "updated_at": "2026-11-09T13:21:02Z",
  "url": "https://research.draconitic.com/paper/f8kk5n8kd8gej",
  "venue": "Astronomy and Astrophysics",
  "versions": []
}