{
  "abstract": "We present JWST/NIRSpec PRISM and G395M grating spectroscopy for AzTEC-1, a massive sub-mm 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. 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 $1245{\\,\\rm km\\,s^{-1}}$ from the systemic narrow line velocity and with FWHM$\\,\\sim2500\\,{\\rm km\\,s^{-1}}$. 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, raising the possibility for a binary supermassive black hole system. In this scenario, we assume that the lower mass black hole hosts a broad line region orbiting a quiescent primary. Evidence for an extended outflow is not found in the 2D spectrum, NIRCam imaging, resolved ALMA observations of dust continuum, or CO, [C II]$_{157\\,μ\\rm m}$ and [N II]$_{\\rm 205\\,μm}$ kinematics. AzTEC-1's high central gas mass surface density and dynamically unstable gas disk indicates that massive gas clouds external to the candidate binary SMBH's orbit might have played a role in stalling infall from $\\sim10$ Myr to $\\sim100$ Myr through dynamical torques, which has been theorized to occur in the nuclei of massive galaxies like AzTEC-1. If the supermassive black hole binary is confirmed, AzTEC-1 would be an excellent laboratory into the astrophysics driving low-frequency gravitational wave detections.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.01711",
  "author_total": 16,
  "authors": [
    {
      "name": "Jed Mckinney"
    },
    {
      "name": "Ansh Gupta"
    },
    {
      "name": "Julian B Munoz"
    },
    {
      "name": "John Chisholm"
    },
    {
      "name": "Caitlin M Casey"
    },
    {
      "name": "Stephanie M. Urbano Stawinski"
    },
    {
      "name": "Olivia Cooper"
    },
    {
      "name": "Erini Lambrides"
    },
    {
      "name": "Hollis Akins"
    },
    {
      "name": "Maximilien Franco"
    },
    {
      "name": "Archana Aravindan"
    },
    {
      "name": "Seiji Fujimoto"
    },
    {
      "name": "Kohei Inayoshi"
    },
    {
      "name": "Andreas L Faisst"
    },
    {
      "name": "Jeyhan S Kartaltepe"
    },
    {
      "name": "Michael Boylan-Kolchin"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/bjymht3km60pv.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.01711",
  "fulltext_url": null,
  "id": "bjymht3km60pv",
  "issns": [],
  "landing_url": "https://hal.science/hal-05758423v1",
  "language": "en",
  "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"
    ],
    [
      "hal",
      "0.phys"
    ],
    [
      "hal",
      "1.phys.astr"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7207696289",
  "pdf_url": "https://arxiv.org/pdf/2609.01711",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/bjymht3km60pv.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:17:37Z",
      "native_id": "hal-05758423",
      "source": "hal",
      "url": "https://hal.science/hal-05758423v1"
    },
    {
      "first_seen": "2026-10-30T12:18:16Z",
      "native_id": "2609.01711",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.01711"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.CO",
      "subfield": "cosmology"
    },
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    },
    {
      "field": "physics",
      "origin": "hal:0.phys",
      "subfield": "general"
    }
  ],
  "title": "JWST Reveals a Candidate Supermassive Black Hole Binary at z=4.3 in the Brightest Sub-millimeter Galaxy in COSMOS-Web",
  "title_text": "JWST Reveals a Candidate Supermassive Black Hole Binary at z=4.3 in the Brightest Sub-millimeter Galaxy in COSMOS-Web",
  "type": "preprint",
  "updated_at": "2026-10-30T12:18:16Z",
  "url": "https://research.draconitic.com/paper/bjymht3km60pv",
  "venue": "HAL",
  "versions": []
}