Where Galaxies Go to Die: The Environments of Massive Quiescent Galaxies at 3 < z < 5

@article{mcconachie2026where,
  title = {{Where Galaxies Go to Die: The Environments of Massive Quiescent Galaxies at 3 < z < 5}},
  author = {Ian McConachie and Anna de Graaff and Michael V. Maseda and Joel Leja and Yunchong Zhang and David J. Setton and Rachel Bezanson and Leindert A. Boogaard and Gabriel Brammer and Nikko J. Cleri and Olivia R. Cooper and Karl Glazebrook and Rashmi Gottumukkala and Jenny E. Greene and Andy D. Goulding and Michaela Hirschmann and Gourav Khullar and Ivo Labbe and Zach Lewis and Jorryt Matthee and Tim B. Miller and Rohan P. Naidu and Themiya Nanayakkara and Erica J. Nelson and Pascal A. Oesch and Sedona H. Price and Katherine A. Suess and Bingjie Wang and Katherine E. Whitaker and Christina C. Williams},
  journal = {The Astrophysical Journal},
  year = {2026},
  month = nov,
  doi = {10.3847/1538-4357/aea6b5},
  url = {https://iopscience.iop.org/article/10.3847/1538-4357/aea6b5},
  note = {CC BY 4.0},
}

TY  - JOUR
TI  - Where Galaxies Go to Die: The Environments of Massive Quiescent Galaxies at 3 < z < 5
AU  - Ian McConachie
AU  - Anna de Graaff
AU  - Michael V. Maseda
AU  - Joel Leja
AU  - Yunchong Zhang
AU  - David J. Setton
AU  - Rachel Bezanson
AU  - Leindert A. Boogaard
AU  - Gabriel Brammer
AU  - Nikko J. Cleri
AU  - Olivia R. Cooper
AU  - Karl Glazebrook
AU  - Rashmi Gottumukkala
AU  - Jenny E. Greene
AU  - Andy D. Goulding
AU  - Michaela Hirschmann
AU  - Gourav Khullar
AU  - Ivo Labbe
AU  - Zach Lewis
AU  - Jorryt Matthee
AU  - Tim B. Miller
AU  - Rohan P. Naidu
AU  - Themiya Nanayakkara
AU  - Erica J. Nelson
AU  - Pascal A. Oesch
AU  - Sedona H. Price
AU  - Katherine A. Suess
AU  - Bingjie Wang
AU  - Katherine E. Whitaker
AU  - Christina C. Williams
PY  - 2026
DA  - 2026/11/02
JO  - The Astrophysical Journal
DO  - 10.3847/1538-4357/aea6b5
UR  - https://iopscience.iop.org/article/10.3847/1538-4357/aea6b5
AB  - At low redshift, massive quiescent galaxies (MQGs) are most frequently found in massive, rich galaxy clusters, but at high redshift the trend is less clear. Here, we present spectroscopic evidence of the effects of environment on the formation and assembly of high-redshift MQGs. We identify 26 (9) log ( M * / M ⊙ ) ≥ 10.5 ( 10.0 ≤ log ( M * / M ⊙ ) < 10.5 ) spectroscopically confirmed quiescent galaxies in the UDS and EGS fields at 3 < z < 5 with NIRSpec spectroscopy from the Red Unknowns: Bright Infrared Extragalactic Spectroscopic (RUBIES) survey and other public JWST programs. We measure the density contrast in these fields by applying a Monte Carlo Voronoi tessellation density-mapping technique to photometric and spectroscopic redshifts of m F444W < 27.5 sources. We robustly detect 19 massive overdense peaks with log ( M Peak / M ⊙ ) ≥ 13 and seven extended massive protoclusters ( log ( M Struct / M ⊙ ) ≥ 13.85 ). We observe that MQGs are preferentially found in these massive peaks and within these massive structures: ≈50% of MQGs are found in massive peaks, compared to ≈25% of massive star-forming galaxies (MSFGs), and quiescent fractions are higher in these regions than in the coeval field. We show that when all stellar mass is assumed to form in situ, the inferred masses of MQG progenitors are significantly higher than those of high- z massive galaxies in observations or simulations. Accounting for ex situ star formation and scaling merger rates by the local galaxy overdensity significantly lessens this tension, which indicates that ex situ star formation plays a key role in MQG mass assembly in overdense environments.
SN  - 1538-4357
SN  - 0004-637X
ER  -