Webb COSMOS-Web maps cosmic web

The University of California, Riverside said on May 11 that astronomers using the James Webb Space Telescope had produced the most detailed map yet of the cosmic web, the network of filaments, sheets and voids that links galaxies across the universe. The work used data from COSMOS-Web, the largest JWST survey so far, and traced large-scale structure back to redshift 7, when the universe was less than 1 billion years old. (news.ucr.edu) (arxiv.org) Hossein Hatamnia, a graduate student at UC Riverside and lead author of the study, said the map lets researchers follow galaxies in cluster and filamentary environments across cosmic time. (cosmos2025.iap.fr) The paper, “Large-scale Structure in COSMOS-Web: Tracing Galaxy Evolution in the Cosmic Web up to z ∼ 7 with the Largest JWST Survey,” was published in The Astrophysical Journal in 2026. ### How far back does this map actually reach? Redshift 7 is the study’s stated limit for its large-scale structure reconstruction, based on about 160,000 galaxies with robust photometric redshifts. (news.ucr.edu) The authors said COSMOS-Web provides mass completeness to about log(M*/M⊙) 8.7 at z∼7, giving what they described as a first view of how environment shaped galaxy evolution from the epoch of reionization onward. ScienceDaily’s summary of the work said the survey traced the network over nearly 14 billion years of cosmic history, while the UC Riverside release said the map reached back to when the universe was about 1 billion years old. (news.ucr.edu) Those descriptions refer to the same broad span from the nearby universe to the early universe. ### What is COSMOS-Web, and why was it suited to this job? COSMOS-Web is a 255-hour JWST Cycle 1 treasury program that maps a contiguous 0.6 square degree area with NIRCam and a non-contiguous 0.2 square degree area with MIRI in parallel. The survey was designed to capture roughly 1 million galaxies across cosmic time, according to the project overview. (arxiv.org) Caitlin Casey and Jeyhan Kartaltepe, the survey’s principal investigators, said in the overview paper that COSMOS-Web was built to study reionization, massive galaxy evolution and dark matter through a combination of width and depth. (sciencedaily.com) That wide field is part of what allowed researchers to identify filaments, dense nodes and voids rather than only isolated distant galaxies. ### What did the researchers say they found inside the web? The Astrophysical Journal paper said stellar mass correlates positively with environmental density at all redshifts in the sample, with stronger effects for quiescent galaxies at z≲2.5. (cosmos.astro.caltech.edu) At higher redshifts, between about 2.5 and 5.5, the authors said that trend is concentrated in extreme overdense regions consistent with early mass assembly in protocluster environments. The same paper said star-formation trends varied by galaxy type and epoch. For quiescent galaxies, star-formation rate showed a negative trend with density at z≲1.2 and reversed at z≳1.8, while star-forming galaxies showed a mild positive correlation up to about z∼5.5. (iopscience.iop.org) The authors said those results indicate mass-driven processes dominate at high redshift, with environmental quenching becoming stronger for lower-mass galaxies at later times. ### Why does Webb show this differently from earlier surveys? Bahram Mobasher, a UC Riverside astronomer and co-author, said in the university release that the large-scale structure identified from JWST data is more informative than earlier maps of the same sky region from the Hubble Space Telescope. (arxiv.org) He said side-by-side comparisons show that earlier-generation data smoothed over structures that Webb can now resolve more clearly. JWST’s role in that improvement is tied to survey design as well as sensitivity. COSMOS-Web combines wide-area infrared imaging with photometric catalogs and redshift estimates over the same field, giving researchers enough depth and area to reconstruct density maps out to high redshift. (arxiv.org) ### Where can other researchers see or use the data next? The COSMOS-Web public data release page says the project hosts reduced mosaics, photometric catalogs, photometric redshifts, physical properties for about 780,000 galaxies and an interactive map viewer over the full field. The same page lists large-scale structure density maps up to z=7 among its additional data products. (news.ucr.edu) On May 4, 2026, the release page said the catalog was updated to version 1.1 and multi-band morphological measurements were added. UC Riverside said the team also released the pipeline used to build the map, the galaxy catalog and a video showing the web evolving across billions of years. (cosmos.astro.caltech.edu) (cosmos2025.iap.fr)