JWST maps 164,000 galaxies

NASA’s James Webb Space Telescope data underpins a new map of the cosmic web that researchers say is the most detailed yet assembled from the observatory’s largest survey field. A team led by University of California, Riverside researchers said on May 11 that it used the COSMOS-Web survey to trace the distribution of more than 164,000 galaxies across 13.7 billion years of cosmic history. (news.ucr.edu) The work appears in *The Astrophysical Journal*, according to the paper abstract and the university’s release. The map follows galaxy structure back to a time when the universe was about 1 billion years old, the researchers said. (sciencedaily.com) ### How did the team get from galaxy images to a map of the cosmic web? (physics.ucsb.edu) The study titled “Large-Scale Structure in COSMOS-Web: Tracing Galaxy Evolution in the Cosmic Web up to z ∼ 7 with the Largest JWST Survey” says the team reconstructed large-scale structure from 160,000 galaxies with robust photometric redshifts. The broader news releases describing the result say the map traces more than 164,000 galaxies, reflecting the survey-scale dataset used to chart dense regions, filaments and voids. COSMOS-Web was designed as a wide-and-deep JWST program rather than a narrow deep field. NASA said in 2021 that the survey would map 0.6 square degrees of sky with NIRCam and a smaller 0.2 square degrees with MIRI, while the COSMOS collaboration later released imaging and a catalog of nearly 800,000 galaxies from the field in June 2025. (news.ucr.edu) ### Why is COSMOS-Web different from earlier deep-space maps? JWST’s infrared instruments let astronomers detect faint, distant galaxies that earlier observatories could not see as clearly, according to NASA and the UC Riverside release. Hatamnia said COSMOS-Web was built “from the start” to provide the wide and deep view needed to see the cosmic web across time. (arxiv.org) Caitlin Casey, a COSMOS collaboration co-leader at the University of California, Santa Barbara, said when the imaging release was announced in 2025 that the project aimed to capture not only very distant galaxies but also the environments where they lived. That wider field is what allows astronomers to place individual galaxies inside filaments, clusters and voids instead of treating them as isolated objects. (science.nasa.gov) ### What does the new map actually show? The UC Riverside release describes the visualization as a slice through the COSMOS-Web cosmic-web map spanning nearly 14 billion years of cosmic history. In that rendering, bright yellow regions mark dense clusters and filaments, while darker regions mark the more empty voids between them. (news.ucr.edu) The paper says the team used the reconstruction to study galaxy evolution in different environments up to redshift 7. The authors report that stellar mass correlates positively with density at all redshifts examined, with stronger effects for star-forming galaxies than for quiescent ones. (physics.ucsb.edu) ### Why are astronomers focusing on “environment” here? The COSMOS-Web overview published on arXiv in 2022 said one of the survey’s main goals was to study galaxy properties as a function of environment and to detect filamentary structure in galaxy distributions. That means the map is not only a picture of where galaxies are, but also a framework for comparing how galaxies change in crowded and sparse parts of the universe. (news.ucr.edu) Bahram Mobasher and co-authors said in the large-scale-structure paper that the reconstruction is meant to trace environmentally driven galaxy evolution. That interpretation comes from the authors, who frame the map as a tool for linking galaxy growth to the larger network of filaments, nodes and voids. (arxiv.org) ### Where can researchers go next with this dataset? The COSMOS collaboration has already made public imaging and galaxy catalogs from the JWST field through its 2025 open-data release, and JWST observations are also accessible through MAST, the mission archive. The new large-scale-structure work adds a map and density reconstruction that other teams can use to target follow-up studies with JWST and with observatories working at other wavelengths. (arxiv.org) The next step is likely to come from named survey participants already attached to the field. Casey and Kartaltepe co-lead the broader COSMOS collaboration, while Hatamnia and Mobasher led the new cosmic-web analysis, according to the paper and university release. (arxiv.org) (physics.ucsb.edu)