DeepDive: Simultaneous Formation of Massive Quiescent Galaxies in High-redshift Galaxy Overdensities

@article{kakimoto2026deepdive,
  title = {{DeepDive: Simultaneous Formation of Massive Quiescent Galaxies in High-redshift Galaxy Overdensities}},
  author = {Takumi Kakimoto and Masayuki Tanaka and Kei Ito and Francesco Valentino and Makoto Ando and Gabriel Brammer and Massissilia L. Hamadouche and Vasily Kokorev and Jacqueline Antwi-Danso and William M. Baker and Daniel Ceverino and Andreas L. Faisst and Marion Farcy and Michaela Hirschmann and Christian Kragh Jespersen and Mariko Kubo and Allison W. S. Man and Masato Onodera and Rhythm Shimakawa and Sune Toft and John R. Weaver and Po-Feng Wu and Pengpei 芃佩 Zhu 朱},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = oct,
  doi = {10.3847/1538-4357/aea69d},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea69d},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - DeepDive: Simultaneous Formation of Massive Quiescent Galaxies in High-redshift Galaxy Overdensities
AU  - Takumi Kakimoto
AU  - Masayuki Tanaka
AU  - Kei Ito
AU  - Francesco Valentino
AU  - Makoto Ando
AU  - Gabriel Brammer
AU  - Massissilia L. Hamadouche
AU  - Vasily Kokorev
AU  - Jacqueline Antwi-Danso
AU  - William M. Baker
AU  - Daniel Ceverino
AU  - Andreas L. Faisst
AU  - Marion Farcy
AU  - Michaela Hirschmann
AU  - Christian Kragh Jespersen
AU  - Mariko Kubo
AU  - Allison W. S. Man
AU  - Masato Onodera
AU  - Rhythm Shimakawa
AU  - Sune Toft
AU  - John R. Weaver
AU  - Po-Feng Wu
AU  - Pengpei 芃佩 Zhu 朱
PY  - 2026
DA  - 2026/10/22
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea69d
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea69d
AB  - 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.
SN  - 0004-637X
SN  - 1538-4357
ER  -