paper

COSMOS2025: A Machine Learning Census of Massive Quiescent Galaxies at

arXiv:2607.13269 · doi:10.3847/1538-4357/ae8b9b

Abstract

The existence of massive quiescent galaxies at high redshifts () strongly constrains the rapid quenching mechanisms in galaxy evolution models. We present a machine learning framework to identify massive () quiescent galaxies at in the COSMOS2025 catalog. We train a \texttt{CatBoostClassifier} on mock photometry from the Santa Cruz semi-analytic models (SAMs), incorporating key JWST NIRCam bands and realistic noise to transfer the SAM-derived quiescent label (based on specific star-formation rate) to the observational space. When validated against the SAM ground truth, our classifier achieves a significantly higher recall (completeness) of 78\% (compared to 53\% for spectral energy distribution (SED)-fitting), while maintaining a high purity of 82\%. Applied to the COSMOS2025 sample, and assuming the SAM definition of quiescence transfers to the real Universe, the model identifies 1111 quiescent candidates, a population 2.6 times larger than the 427 candidates identified via the catalog's simple SED-fitting configuration. Under the SAM definition of quiescence, this consistent pattern of high purity but poor completeness suggests that the SED-fitting methods, constrained by simplified parametric star-formation histories, may miss a significant fraction of the quiescent population, likely galaxies in crucial transitional evolutionary stages. The trained classifier and classified COSMOS2025 sample are publicly available.

17 pages, 12 figures, 6 tables, Accepted for Publication in ApJ

References in corpus (73)