{"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/insights-from-hst-into-ultra-massive-galaxies","title":"Insights from HST into Ultra-Massive Galaxies and Early-Universe Cosmology","arxiv_id":"2305.07049","date":"2023-05-11","proceeding":null,"authors":["Nashwan Sabti","Julian B. Muñoz","Marc Kamionkowski"],"abstract":"The early-science observations made by the James Webb Space Telescope (JWST) have revealed an excess of ultra-massive galaxy candidates that appear to challenge the standard cosmological model ($\\Lambda$CDM). Here, we argue that any modifications to $\\Lambda$CDM that can produce such ultra-massive galaxies in the early Universe would also affect the UV galaxy luminosity function (UV LF) inferred from the Hubble Space Telescope (HST). The UV LF covers the same redshifts ($z\\approx 7-10$) and host-halo masses $(M_\\mathrm{h}\\approx 10^{10}-10^{12}\\, M_\\odot$) as the JWST candidates, but tracks star-formation rate rather than stellar mass. We consider beyond-$\\Lambda$CDM power-spectrum enhancements and show that any departure large enough to reproduce the abundance of ultra-massive JWST candidates is in conflict with the HST data. Our analysis, therefore, severely disfavors a cosmological explanation for the JWST abundance problem. Looking ahead, we determine the maximum allowable stellar-mass function and provide projections for the high-$z$ UV LF given our constraints on cosmology from current HST data.","url_abs":"https://arxiv.org/abs/2305.07049v2","url_pdf":"https://arxiv.org/pdf/2305.07049v2.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":"insights-from-hst-into-ultra-massive-galaxies","repo_url":"https://github.com/nnssa/gallumi_public","is_official":1,"mentioned_in_paper":1,"mentioned_in_github":0,"framework":"none","reach":null}],"tasks":[],"methods":[],"datasets_introduced":[],"methods_introduced":[],"results":[],"syntology":{"syntology_url":null,"atlas_url":null,"mcp":null,"developers":"https://syntology.ai/developers"},"arxiv_metadata":null,"syntology_extracted_results":null}