{ "abstract": "We report on the spectroscopic confirmation of overdense regions of massive quiescent galaxies (QGs) in the early Universe with JWST/NIRSpec. Based on data from the DeepDive NIRSpec program and archival data from the Dawn JWST Archive, we confirm three QGs in the vicinity of Jekyll and Hyde, a pair of massive QG and a dusty star-forming galaxy, at z = 3.71 and two QGs around SXDS-27434 at z = 4.01. According to the analysis of galaxy number density with photometric redshifts, Jekyll and Hyde (SXDS-27434) are in an overdense region, where the number density of galaxies is three (four) times higher than the average in the COSMOS (SXDS) field. SED fitting suggests that most of the QGs follow similar star formation histories and have consistent formation and quenching epochs. The same trend is observed in other protoclusters hosting QGs that were already identified by ground-based telescopes, indicating that the large-scale environment plays an important role in the formation of QGs. In addition, JWST spectra reveal a broad H α emission line from SXDS-27434 and faint emission lines from the other three QGs, which are identified as AGN-driven based on their emission line ratios. The overdensity is also reproduced by the Illustris TNG300 simulation at z = 3.71, in which the member QGs also have similar quenching epochs. These results are consistent with a scenario in which the large-scale structure enhances merger activity and/or gas accretion and triggers AGN feedback, thereby driving simultaneous formation and quenching of QGs in the overdensity.", "abstract_shown": true, "affiliations": [ "The Graduate University for Advanced Studies", "National Astronomical Observatory of Japan", "Cosmic Dawn Center (DAWN)", "Technical University of Denmark", "The University of Tokyo", "University of Copenhagen", "University of Massachusetts", "The University of Texas at Austin", "University of Toronto", "Dunlap Institute for Astronomy and Astrophysics", "Universidad Autonoma de Madrid", "IPAC", "Institute for Physics", "Princeton University", "Kwansei Gakuin University", "Tohoku University", "University of British Columbia", "Subaru Telescope", "Waseda University", "MIT Kavli Institute for Astrophysics and Space Research", "National Taiwan University" ], "article_type": null, "arxiv": null, "author_total": 23, "authors": [ { "affs": [ 0, 1 ], "name": "Takumi Kakimoto", "orcid": "0000-0003-2918-9890" }, { "affs": [ 0, 1 ], "name": "Masayuki Tanaka", "orcid": "0000-0002-5011-5178" }, { "affs": [ 2, 3 ], "name": "Kei Ito", "orcid": "0000-0002-9453-0381" }, { "affs": [ 2, 3 ], "name": "Francesco Valentino", "orcid": "0000-0001-6477-4011" }, { "affs": [ 1, 4 ], "name": "Makoto Ando", "orcid": "0000-0002-4225-4477" }, { "affs": [ 2, 5 ], "name": "Gabriel Brammer", "orcid": "0000-0003-2680-005X" }, { "affs": [ 6 ], "name": "Massissilia L. Hamadouche", "orcid": "0000-0001-6763-5551" }, { "affs": [ 7 ], "name": "Vasily Kokorev", "orcid": "0000-0002-5588-9156" }, { "affs": [ 8, 9 ], "name": "Jacqueline Antwi-Danso", "orcid": "0000-0002-0243-6575" }, { "affs": [ 5 ], "name": "William M. Baker", "orcid": "0000-0003-0215-1104" }, { "affs": [ 10 ], "name": "Daniel Ceverino", "orcid": "0000-0002-8680-248X" }, { "affs": [ 11 ], "name": "Andreas L. Faisst", "orcid": "0000-0002-9382-9832" }, { "affs": [ 12 ], "name": "Marion Farcy", "orcid": "0000-0002-5228-2244" }, { "affs": [ 12 ], "name": "Michaela Hirschmann", "orcid": "0000-0002-3301-3321" }, { "affs": [ 13 ], "name": "Christian Kragh Jespersen", "orcid": "0000-0002-8896-6496" }, { "affs": [ 14, 15 ], "name": "Mariko Kubo", "orcid": "0000-0002-7598-5292" }, { "affs": [ 16 ], "name": "Allison W. S. Man", "orcid": "0000-0003-2475-124X" }, { "affs": [ 0, 17 ], "name": "Masato Onodera", "orcid": "0000-0003-3228-7264" }, { "affs": [ 18 ], "name": "Rhythm Shimakawa", "orcid": "0000-0003-4442-2750" }, { "affs": [ 2, 5 ], "name": "Sune Toft", "orcid": "0000-0003-3631-7176" }, { "affs": [ 19 ], "name": "John R. Weaver", "orcid": "0000-0003-1614-196X" }, { "affs": [ 20 ], "name": "Po-Feng Wu", "orcid": "0000-0002-9665-0440" }, { "affs": [ 2, 3 ], "name": "Pengpei 芃佩 Zhu 朱", "orcid": "0000-0002-6768-8335" } ], "bibtex": "https://research.draconitic.com/paper/f3qr81skychpd.bib", "cited_by": 1, "doi": "10.3847/1538-4357/aea69d", "fulltext_url": null, "id": "f3qr81skychpd", "issns": [ "0004-637X", "1538-4357" ], "landing_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea69d", "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": [ [ "openalex", "3103|Galaxies: Formation, Evolution, Phenomena" ] ], "openalex": "W7155554427", "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea69d/pdf", "pmcid": null, "pmid": null, "published": "2026-10-22", "publisher": "American Astronomical Society", "ris": "https://research.draconitic.com/paper/f3qr81skychpd.ris", "sources": [ { "first_seen": "2026-10-30T12:18:11Z", "native_id": "10.3847/1538-4357/aea69d", "source": "crossref", "url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea69d" } ], "subjects": [ { "field": "astronomy", "origin": "openalex:3103|Galaxies: Formation, Evolution, Phenomena", "subfield": "galaxies" } ], "title": "DeepDive: Simultaneous Formation of Massive Quiescent Galaxies in High-redshift Galaxy Overdensities", "title_text": "DeepDive: Simultaneous Formation of Massive Quiescent Galaxies in High-redshift Galaxy Overdensities", "type": "peer-reviewed", "updated_at": "2026-10-30T12:18:11Z", "url": "https://research.draconitic.com/paper/f3qr81skychpd", "venue": "The Astrophysical Journal", "versions": [] }