{"about":{"site":"https://codewithpapers.app","non_affiliation":"Code with Papers and Syntology are not affiliated with, endorsed by, or sponsored by Papers with Code, Meta, or the pwc-archive mirror.","licence":"CC BY-SA 4.0","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","attribution":"https://codewithpapers.app/attribution","modified":"archive material modified by Syntology; see the attribution page"},"url":"/paper/cosmos2020-exploring-the-dawn-of-quenching","title":"COSMOS2020: Exploring the dawn of quenching for massive galaxies at 3 < z < 5 with a new colour selection method","arxiv_id":"2302.10934","date":"2023-02-21","proceeding":null,"authors":["Katriona M. L. Gould","Gabriel Brammer","Francesco Valentino","Katherine E. Whitaker","John R. Weaver","Claudia del P. Lagos","Francesca Rizzo","Maximilien Franco","Bau-Ching Hseih","Olivier Ilbert","Shuowen Jin","Georgios Magdis","Henry J. McCracken","Bahram Mobasher","Marko Shuntov","Charles L. Steinhardt","Victoria Strait","Sune Toft"],"abstract":"We select and characterise a sample of massive (log(M$_{*}/$M$_{\\odot})>10.6$) quiescent galaxies (QGs) at $3<z<5$ in the latest COSMOS2020 catalogue. QGs are selected using a new rest-frame colour selection method, based on their probability of belonging to the quiescent group defined by a Gaussian Mixture Model (GMM) trained on rest-frame colours ($NUV-U, U-V, V-J$) of similarly massive galaxies at $2<z<3$. We calculate the quiescent probability threshold above which a galaxy is classified as quiescent using simulated galaxies from the SHARK semi-analytical model. We find that at $z\\geq3$ in SHARK, the GMM/$NUVU-VJ$ method out-performs classical rest-frame $UVJ$ selection and is a viable alternative. We select galaxies as quiescent based on their probability in COSMOS2020 at $3<z<5$, and compare the selected sample to both $UVJ$ and $NUVrJ$ selected samples. We find that although the new selection matches $UVJ$ and $NUVrJ$ in number, the overlap between colour selections is only $\\sim50-80\\%$, implying that rest-frame colour commonly used at lower redshifts selections cannot be equivalently used at $z>3$. We compute median rest-frame SEDs for our sample and find the median quiescent galaxy at $3<z<5$ has a strong Balmer/4000 Angstrom break, and residual $NUV$ flux indicating recent quenching. We find the number densities of the entire quiescent population (including post-starbursts) more than doubles from $3.5\\pm2.2\\times10^{-6}$ Mpc$^{-3}$ at $4<z<5$ to $1.4\\pm0.4\\times10^{-5}$ Mpc$^{-3}$ at $3<z<4$, confirming that the onset of massive galaxy quenching occurs as early as $3<z<5$.","url_abs":"https://arxiv.org/abs/2302.10934v1","url_pdf":"https://arxiv.org/pdf/2302.10934v1.pdf","source":{"archive":"pwc-archive (Hugging Face), CC BY-SA 4.0","snapshot":"2025-07-28","licence_url":"https://creativecommons.org/licenses/by-sa/4.0/legalcode","row_kind":"links_only","authors_date_abstract":"arXiv metadata, CC0 1.0 (https://info.arxiv.org/help/license), from the Kaggle arXiv metadata snapshot of 2026-09-12"},"code_links":[{"paper_slug":"cosmos2020-exploring-the-dawn-of-quenching","repo_url":"https://github.com/kmlgould/gmm-quiescent","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}