{
  "abstract": "UV-bright galaxies in the early Universe provide important constraints on the rapid build-up of stellar mass and the sources responsible for cosmic reionization. However, the physical processes that drive their high UV luminosities remain unclear. Here we report JWST/MIRI LRS spectroscopy of GHZ8, a UV-bright galaxy at z=10.23 with a magnification $μ=1.23$. The spectrum shows a $\\sim 5σ$ detection for the $\\rm Hβ$-[OIII] complex and $\\sim 4σ$ for $\\rm Hα$ line, with fluxes of $3.2\\pm0.9\\times10^{-18}$ and $\\rm 1.7\\pm0.4\\times10^{-18}\\,erg\\,s^{-1}\\,cm^{-2}$, respectively. Based on JWST/NIRCam imaging, we find that GHZ8 consists of two components separated only by 0.16\" ($\\approx600$ pc): a bright, extended main component and a faint, compact southeastern clump, hereafter referred to as GHZ8-main and GHZ8-SE. Through morphological decomposition, we find demagnified $M_{UV}=-19.91\\pm0.10$ and $-18.03\\pm0.15$ mag for GHZ8-main and GHZ8-SE, with blue UV slopes of $β_{UV}=-2.53\\pm0.22$ and $-3.45\\pm0.49$, respectively, indicating that both components host young stellar populations. In particular, the extremely blue UV continuum of GHZ8-SE requires an extremely young, ISM-poor stellar population with a high ionizing photon escape fraction, $f_{esc}= 0.6-1.0$. Combining the UV and $\\rm Hα$ luminosities with the results from the spectro-photometric SED fitting, we constrain the star-formation activity of GHZ8-main, and find either a recent, short-lived burst of star formation that is now in its final phases, or continuous star formation over a relatively short period ($<50\\,{\\rm Myr}$). GHZ8 therefore provides observational evidence for bursty star formation in a UV-bright galaxy. Globally, GHZ8 may be undergoing a merger-induced starburst, although deeper imaging or spatially resolved kinematic information is required for a more definitive interpretation.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.40633",
  "author_total": 29,
  "authors": [
    {
      "name": "Ruqiu Lin"
    },
    {
      "name": "Jorge Zavala"
    },
    {
      "name": "Javier Álvarez-Márquez"
    },
    {
      "name": "Luis Colina"
    },
    {
      "name": "Marco Castellano"
    },
    {
      "name": "Adriano Fontana"
    },
    {
      "name": "Paola Santini"
    },
    {
      "name": "Lorenzo Napolitano"
    },
    {
      "name": "Sarah Kendrew"
    },
    {
      "name": "Alejandro Crespo Gómez"
    },
    {
      "name": "Victoria Salazar"
    },
    {
      "name": "Abdurro'uf"
    },
    {
      "name": "Stefano Carniani"
    },
    {
      "name": "Tiger Hsiao"
    },
    {
      "name": "Yuichi Harikane"
    },
    {
      "name": "Mahmoud Hamed"
    },
    {
      "name": "Takuya Hashimoto"
    },
    {
      "name": "Akio Inoue"
    },
    {
      "name": "Danial Langeroodi"
    },
    {
      "name": "Rui Marques-Chaves"
    },
    {
      "name": "Ikki Mitsuhashi"
    },
    {
      "name": "Yurina Nakazato"
    },
    {
      "name": "Borja Pérez-Díaz"
    },
    {
      "name": "Pierluigi Rinaldi"
    },
    {
      "name": "Carlota Prieto-Jiménez"
    },
    {
      "name": "Ana Varo-O'Ferrall"
    },
    {
      "name": "Fang-Ting Yuan"
    },
    {
      "name": "Shuairu Zhu"
    },
    {
      "name": "Zhen-Ya Zheng"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/5c0bwrwm1daxc.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.40633",
  "fulltext_url": null,
  "id": "5c0bwrwm1daxc",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.40633",
  "language": null,
  "licence": "CC-BY-NC-SA-4.0",
  "licence_label": "CC BY-NC-SA 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by-nc-sa/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.GA"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.40633",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-29",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/5c0bwrwm1daxc.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:28Z",
      "native_id": "2610.40633",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.40633"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "PRISMS GHZ8: Evidence for a Young Burst and Potential Merger Activity at z=10.23",
  "title_text": "PRISMS GHZ8: Evidence for a Young Burst and Potential Merger Activity at z=10.23",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:47Z",
  "url": "https://research.draconitic.com/paper/5c0bwrwm1daxc",
  "venue": "arXiv",
  "versions": []
}