{
  "abstract": "We report JWST observations of a $z_{\\rm spec}=5.196$ compact group of three strongly lensed low-mass galaxies ($M_\\star \\sim 10^{6-7} M_\\odot$ each) whose small line-of-sight velocity offsets (from $-120\\pm100$ to $+160\\pm110$ km s$^{-1}$) and projected separations ($\\sim2$ kpc) suggest that they are undergoing merging. On the basis of abundance-matching arguments, the trio appear to be destined to evolve into a Milky Way-mass galaxy by the present day. Our spectrophotometric analysis suggests that the stellar mass growth of this system is not simply just due to the merging of its components; rather, it is being dramatically enhanced by intense bursts of star formation. Presumably initiated by tidally-induced gas inflows, these star-forming bursts boost the mass growth $2.6\\pm0.5$ times that expected in straightforward merging of the existing stellar masses. These spectroscopic observations thus not only demonstrate that hierarchical assembly remains a viable formation channel in the early assembly phases of present-day massive galaxy, but also that interaction-induced bursts of star formation are a major accelerator of this assembly process.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.19687",
  "author_total": 17,
  "authors": [
    {
      "name": "Yoshihisa Asada"
    },
    {
      "name": "Marcin Sawicki"
    },
    {
      "name": "Guillaume Desprez"
    },
    {
      "name": "Jon Judez"
    },
    {
      "name": "Marusa Bradac"
    },
    {
      "name": "Kartheik Iyer"
    },
    {
      "name": "Nicholas S. Martis"
    },
    {
      "name": "Adam Muzzin"
    },
    {
      "name": "Gael Noirot"
    },
    {
      "name": "Ghassan T. E. Sarrouh"
    },
    {
      "name": "Chris J. Willott"
    },
    {
      "name": "Jacqueline Antwi-Danso"
    },
    {
      "name": "Seiji Fujimoto"
    },
    {
      "name": "Danilo Marchesini"
    },
    {
      "name": "Vladan Markov"
    },
    {
      "name": "Luke Robbins"
    },
    {
      "name": "Visal Sok"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/64nfqxcxz99ga.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.19687",
  "fulltext_url": null,
  "id": "64nfqxcxz99ga",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.19687",
  "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.GA"
    ],
    [
      "openalex",
      "3103|Galaxies: Formation, Evolution, Phenomena"
    ]
  ],
  "openalex": "W7213590074",
  "pdf_url": "https://arxiv.org/pdf/2609.19687",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-17",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/64nfqxcxz99ga.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:22:19Z",
      "native_id": "2609.19687",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.19687"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.GA",
      "subfield": "galaxies"
    }
  ],
  "title": "Early steps in the hierarchical assembly of a Milky Way-mass galaxy 1 Gyr after the Big Bang",
  "title_text": "Early steps in the hierarchical assembly of a Milky Way-mass galaxy 1 Gyr after the Big Bang",
  "type": "preprint",
  "updated_at": "2026-10-30T12:22:19Z",
  "url": "https://research.draconitic.com/paper/64nfqxcxz99ga",
  "venue": "arXiv",
  "versions": []
}