A Census of the 200 Most Massive Galaxies Spectroscopically Observed with JWST at zspec ∼3-15

@misc{xiao2026census,
  title = {{A Census of the 200 Most Massive Galaxies Spectroscopically Observed with JWST at zspec $\sim$3-15}},
  author = {Mengyuan Xiao and Pascal A. Oesch and Longji Bing and Rashmi Gottumukkala and Rui Marques-Chaves and Gabriel Brammer and Miroslava Dessauges-Zavadsky and David Elbaz and Songnan Qi and Anurag Amol Sawarkar and Manuel Aravena and Matthieu Béthermin and Rachel Bezanson and Rychard Bouwens and Caitlin Casey and Pieter van Dokkum and Andreas L. Faisst and Yoshinobu Fudamoto and Anna de Graaff and Olivier Ilbert and Garth Illingworth and Guilaine Lagache and Benjamin Magnelli and Jorryt Matthee and Yurina Nakazato and Daniel Schaerer and Sune Toft and Katherine E. Whitaker and Christina C. Williams},
  howpublished = {arXiv},
  year = {2026},
  month = nov,
  doi = {10.48550/arxiv.2606.30802},
  eprint = {2606.30802},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2606.30802},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - A Census of the 200 Most Massive Galaxies Spectroscopically Observed with JWST at zspec ∼3-15
AU  - Mengyuan Xiao
AU  - Pascal A. Oesch
AU  - Longji Bing
AU  - Rashmi Gottumukkala
AU  - Rui Marques-Chaves
AU  - Gabriel Brammer
AU  - Miroslava Dessauges-Zavadsky
AU  - David Elbaz
AU  - Songnan Qi
AU  - Anurag Amol Sawarkar
AU  - Manuel Aravena
AU  - Matthieu Béthermin
AU  - Rachel Bezanson
AU  - Rychard Bouwens
AU  - Caitlin Casey
AU  - Pieter van Dokkum
AU  - Andreas L. Faisst
AU  - Yoshinobu Fudamoto
AU  - Anna de Graaff
AU  - Olivier Ilbert
AU  - Garth Illingworth
AU  - Guilaine Lagache
AU  - Benjamin Magnelli
AU  - Jorryt Matthee
AU  - Yurina Nakazato
AU  - Daniel Schaerer
AU  - Sune Toft
AU  - Katherine E. Whitaker
AU  - Christina C. Williams
PY  - 2026
DA  - 2026/11/04
PB  - arXiv
DO  - 10.48550/arxiv.2606.30802
UR  - https://arxiv.org/abs/2606.30802
AB  - Massive galaxies provide strong tests of galaxy formation models, yet a comprehensive spectroscopic view of their properties and demographics in the early Universe has remained elusive. Here we present a JWST spectroscopic census of the 200 most massive galaxies at zspec~3-15, selected using an evolving stellar-mass threshold motivated by the halo mass function and anchored at log(Mstar)>10 at z~5. These galaxies represent the top 3% most massive systems among all publicly available prism observations. We derive their physical properties through joint SED fitting of spectroscopy and photometry, and construct a clean massive galaxy sample after removing LRDs and broad-line AGN contaminants. We find that the massive galaxy population evolves strongly with redshift: normal SFGs (Av<1 mag) dominate at z>~6, while dusty SFGs (Av>1 mag) and QGs become more common toward lower redshift. Dust attenuation decreases systematically toward higher redshift. We identify 29 massive QGs, including a population of recently quenched systems whose star formation declined rapidly within the past ~100 Myr. We further show that both the traditional UVJ and recently proposed (ugi)s selections suffer substantial inconsistency with the most massive galaxies at z>3, motivating a revised (ugi)s criterion calibrated using our spectroscopic sample. The inferred formation histories suggest at least two pathways toward quiescence: a dust-enriched pathway linking normal SFGs, dusty SFGs, and QGs, and a more direct pathway connecting normal SFGs and QGs. Massive normal SFGs appear to grow through both relatively gradual and rapid assembly modes. Together, these results suggest that rapid stellar-mass assembly, dust enrichment, and quenching were already shaping the evolutionary pathways of the most massive galaxies within the first billion years after the Big Bang.
ER  -