pop-cosmos: Galaxy size evolution across structural and star-formation classifications in COSMOS-Web
Abstract
Galaxy sizes are correlated with stellar mass and redshift, as characterised by size scaling relations. The inferred forms of these scaling relations are sensitive to how galaxies are classified -- either by their star formation activity (e.g. specific star-formation rate, sSFR) or by their morphology markers (e.g. bulge-to-total ratio, Sérsic index). We combine stellar mass and sSFR estimates from pop-cosmos (a generative model trained on COSMOS2020 Spitzer IRAC Ch.1 <26) with size and morphology measurements from COSMOS-Web, obtaining $99,369$ galaxies. By investigating the size-mass and the size-redshift relations, we show that: (i) the sSFR/morphology splits give quantitatively different slopes, intercepts, and intrinsic scatter behaviour; (ii) intrinsic scatter depends on structural morphology but not on sSFR, which constrains the galaxy-halo connection; (iii) the quiescent and bulge-dominated size-mass relations both show double-power law breaks, but at different pivot masses, indicating that quenching and structural transformation occur on different time-scales; (iv) the morphology-dependent trends are only recoverable from space-based imaging. Further, the quiescent pivot mass M∗ ∼ 1010.7 M⊙ coincides with the mass scale at which active galactic nuclei (AGN, infrared torus) bolometric luminosity fraction peaks in transitioning galaxies, while the bulge-dominated pivot mass M∗ ∼ 1011.1 M⊙ coincides with the halo mass at which AGN-driven baryonic redistribution peaks, which may trace the interval over which AGN feedback ramps from quenching onset to structural transformation.
Related
- AGN Host Galaxies in COSMOS-Web: Linking Structural Evolution and Star Formation Quenching up to z=5
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- Characterising the formation and evolution of S0-galaxies (CaFES-0): Their formation pathways around galaxy clusters
- From short-lived to long-lived clouds: Impact of star formation models on giant molecular cloud evolution in simulations of an NGC 300-like galaxy
BibTeX
@misc{tudorache2026popcosmos,
title = {{pop-cosmos: Galaxy size evolution across structural and star-formation classifications in COSMOS-Web}},
author = {Madalina N. Tudorache and Hiranya V. Peiris and Stephen Thorp and Sinan Deger and Daniel J. Mortlock and Gurjeet Jagwani and Anik Halder and Boris Leistedt and Benedict Van den Bussche and Joel Leja},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2606.28489},
eprint = {2606.28489},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.28489},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - pop-cosmos: Galaxy size evolution across structural and star-formation classifications in COSMOS-Web
AU - Madalina N. Tudorache
AU - Hiranya V. Peiris
AU - Stephen Thorp
AU - Sinan Deger
AU - Daniel J. Mortlock
AU - Gurjeet Jagwani
AU - Anik Halder
AU - Boris Leistedt
AU - Benedict Van den Bussche
AU - Joel Leja
PY - 2026
DA - 2026/10/28
PB - arXiv
DO - 10.48550/arxiv.2606.28489
UR - https://arxiv.org/abs/2606.28489
AB - Galaxy sizes are correlated with stellar mass and redshift, as characterised by size scaling relations. The inferred forms of these scaling relations are sensitive to how galaxies are classified -- either by their star formation activity (e.g. specific star-formation rate, sSFR) or by their morphology markers (e.g. bulge-to-total ratio, Sérsic index). We combine stellar mass and sSFR estimates from pop-cosmos (a generative model trained on COSMOS2020 Spitzer IRAC Ch.1 <26) with size and morphology measurements from COSMOS-Web, obtaining $99,369$ galaxies. By investigating the size-mass and the size-redshift relations, we show that: (i) the sSFR/morphology splits give quantitatively different slopes, intercepts, and intrinsic scatter behaviour; (ii) intrinsic scatter depends on structural morphology but not on sSFR, which constrains the galaxy-halo connection; (iii) the quiescent and bulge-dominated size-mass relations both show double-power law breaks, but at different pivot masses, indicating that quenching and structural transformation occur on different time-scales; (iv) the morphology-dependent trends are only recoverable from space-based imaging. Further, the quiescent pivot mass M_∗ ∼ 10^10.7 M_⊙ coincides with the mass scale at which active galactic nuclei (AGN, infrared torus) bolometric luminosity fraction peaks in transitioning galaxies, while the bulge-dominated pivot mass M_∗ ∼ 10^11.1 M_⊙ coincides with the halo mass at which AGN-driven baryonic redistribution peaks, which may trace the interval over which AGN feedback ramps from quenching onset to structural transformation.
ER -