{
  "abstract": "We present JWST/NIRSpec PRISM and G395M grating spectroscopy for AzTEC-1, a massive submillimeter bright galaxy at z = 4.34 in the COSMOS extragalactic field. The PRISM spectrum reveals strong H α , a significant Balmer break, and no H β detection, indicating a 100–400 Myr old stellar population and high dust attenuation. Baldwin–Phillips–Terlevich (BPT) line ratios indicate the presence of an active galactic nucleus (AGN). Decomposing narrow- and broad-line components, we recover broad, blueshifted H α with a velocity offset of 1245 km s ⁻¹ from the systemic narrow-line velocity and with FWHM ≈ 2500 km s ⁻¹ . AzTEC-1’s smooth morphology and stellar age is suggestive of a past merger-induced starburst period that would have brought in a second supermassive black hole (SMBH), raising the possibility for a binary SMBH system. In this scenario, we assume that the lower-mass black hole (BH) hosts a broad-line region orbiting a quiescent primary. Evidence for an extended outflow is not found in the 2D spectrum, NIRCam imaging, resolved Atacama Large Millimeter/submillimeter Array (ALMA) observations of dust continuum, or CO, [C ii ] 157 μ m , and [N ii ] ₂ 05 μ m kinematics. AzTEC-1’s high central gas-mass surface density and dynamically unstable gas disk indicate that massive gas clouds external to the candidate binary SMBH’s orbit might have played a role in stalling infall from O ( 10 Myr) to O ( 100 Myr) through dynamical torques, which has been theorized to occur in the nuclei of massive galaxies like AzTEC-1. If the SMBH binary is confirmed, AzTEC-1 would be an excellent laboratory into the astrophysics driving low-frequency gravitational-wave detections.",
  "abstract_shown": true,
  "affiliations": [
    "The University of Texas at Austin",
    "University of California Santa Barbara",
    "University of Colorado",
    "NASA-Goddard Space Flight Center",
    "Université Paris-Saclay",
    "University of Toronto",
    "Peking University",
    "Caltech/IPAC",
    "Rochester Institute of Technology"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 16,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Jed McKinney",
      "orcid": "0000-0002-6149-8178"
    },
    {
      "affs": [
        0
      ],
      "name": "Ansh Gupta",
      "orcid": "0000-0003-4242-8606"
    },
    {
      "affs": [
        0
      ],
      "name": "Julian B. Muñoz",
      "orcid": "0000-0002-8984-0465"
    },
    {
      "affs": [
        0
      ],
      "name": "John Chisholm",
      "orcid": "0000-0002-0302-2577"
    },
    {
      "affs": [
        1
      ],
      "name": "Caitlin M. Casey",
      "orcid": "0000-0002-0930-6466"
    },
    {
      "affs": [
        1
      ],
      "name": "Stephanie M. Urbano Stawinski",
      "orcid": "0000-0001-8169-7249"
    },
    {
      "affs": [
        2
      ],
      "name": "Olivia Cooper",
      "orcid": "0000-0003-3881-1397"
    },
    {
      "affs": [
        3
      ],
      "name": "Erini Lambrides",
      "orcid": "0000-0003-3216-7190"
    },
    {
      "affs": [
        0
      ],
      "name": "Hollis Akins",
      "orcid": "0000-0003-3596-8794"
    },
    {
      "affs": [
        4
      ],
      "name": "Maximilien Franco",
      "orcid": "0000-0002-3560-8599"
    },
    {
      "affs": [
        0
      ],
      "name": "Archana Aravindan",
      "orcid": "0000-0001-7578-2412"
    },
    {
      "affs": [
        5
      ],
      "name": "Seiji Fujimoto",
      "orcid": "0000-0001-7201-5066"
    },
    {
      "affs": [
        6
      ],
      "name": "Kohei Inayoshi",
      "orcid": "0000-0001-9840-4959"
    },
    {
      "affs": [
        7
      ],
      "name": "Andreas L. Faisst",
      "orcid": "0000-0002-9382-9832"
    },
    {
      "affs": [
        8
      ],
      "name": "Jeyhan S. Kartaltepe",
      "orcid": "0000-0001-9187-3605"
    },
    {
      "affs": [
        0
      ],
      "name": "Michael Boylan-Kolchin",
      "orcid": "0000-0002-9604-343X"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/e11dhtysat5tg.bib",
  "cited_by": 0,
  "doi": "10.3847/2041-8213/aea0cd",
  "fulltext_url": null,
  "id": "e11dhtysat5tg",
  "issns": [
    "2041-8213",
    "2041-8205"
  ],
  "landing_url": "https://iopscience.iop.org/article/10.3847/2041-8213/aea0cd",
  "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": [
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      "feed-journal",
      "astronomy/general"
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  "pdf_url": "https://iopscience.iop.org/article/10.3847/2041-8213/aea0cd/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-30",
  "publisher": "American Astronomical Society",
  "ris": "https://research.draconitic.com/paper/e11dhtysat5tg.ris",
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      "first_seen": "2026-10-30T18:20:22Z",
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  "subjects": [
    {
      "field": "astronomy",
      "origin": "journal-openalex:3103|Stellar, planetary, and galactic studies",
      "subfield": "stellar"
    }
  ],
  "title": "JWST Reveals a Candidate Supermassive Black Hole Binary at z = 4.3 in the Brightest Submillimeter Galaxy in COSMOS-Web",
  "title_text": "JWST Reveals a Candidate Supermassive Black Hole Binary at z = 4.3 in the Brightest Submillimeter Galaxy in COSMOS-Web",
  "type": "peer-reviewed",
  "updated_at": "2026-11-01T00:20:39Z",
  "url": "https://research.draconitic.com/paper/e11dhtysat5tg",
  "venue": "The Astrophysical Journal Letters",
  "versions": []
}