James Webb reveals cosmic web details

Researchers led by the University of California, Riverside said this month that data from NASA’s James Webb Space Telescope had produced the most detailed map yet of the cosmic web, the large-scale structure linking galaxies across the universe. The work used the COSMOS-Web survey, the biggest James Webb survey so far, to trace more than 164,000 galaxies across nearly 13.7 billion years of cosmic history. The findings were published in *The Astrophysical Journal*, according to UC Riverside and the paper. Science coverage on May 20 and May 21 highlighted the result as a new look at the web’s filaments and voids deep into the early universe. ### What exactly did Webb’s team map? The cosmic web is the universe’s “skeleton-like framework,” made of filaments and sheets of dark matter and gas surrounding near-empty voids, UC Riverside said in its May 11 release. In the new work, astronomers used the distribution of galaxies in COSMOS-Web to reconstruct that large-scale structure over time. (news.ucr.edu) The survey spans a patch of sky about the size of three full moons and was designed specifically to give a wide, deep view of the distant universe. Hossein Hatamnia, a graduate student at UC Riverside and Carnegie Observatories and lead author of the study, said COSMOS-Web was built to let researchers study galaxy evolution “in cluster and filamentary structures across cosmic time.” (news.ucr.edu) ### Why is this being described as a sharper view than before? James Webb’s infrared instruments can detect faint, distant galaxies that earlier telescopes could not see as clearly, the university and ScienceDaily said. That let the team push the map back to when the universe was about one billion years old, and in some reporting, to structures from only a few hundred million years after the Big Bang. (sciencedaily.com) Bahram Mobasher, an astronomer at UC Riverside and a co-author, said “the jump in depth and resolution is truly significant.” He said structures that had looked like single features in earlier data now break into multiple components in Webb observations. ### Where do the “new details” come from? The May 20 heise report said Webb revealed “previously unknown details” of the cosmic web, including structures that had been smoothed over in earlier Hubble-era views. (news.ucr.edu) That account said the new data made it possible to distinguish filaments and other features much more clearly than before. (heise.de) NASA published a related COSMOS dark-matter map in January that used Webb imaging and weak gravitational lensing to show new clumps of dark matter at higher resolution than earlier Hubble maps. That is a separate result, but it comes from the same broader COSMOS field and shows how Webb’s higher-resolution data are refining large-scale structure studies. (heise.de) ### Did Webb directly see dark matter filaments? The study describes the cosmic web as being shaped by dark matter and gas, but dark matter itself remains invisible. Researchers infer that structure from the arrangement of galaxies and, in other COSMOS analyses, from gravitational lensing effects on background light. The January NASA explanation said dark matter does not emit or absorb light and is mapped through its gravitational influence. (science.nasa.gov) In this case, that means the new cosmic-web picture is a reconstruction from observable tracers, not a direct photograph of dark matter threads. ### What comes next from COSMOS-Web? The paper is titled *Large-scale Structure in COSMOS-Web: Tracing Galaxy Evolution in the Cosmic Web up to z ∼ 7 with the Largest JWST Survey*. (sciencedaily.com) The author list includes Hatamnia, Mobasher, Jeyhan S. Kartaltepe, Caitlin M. Casey and other COSMOS-Web collaborators. UC Riverside said the dataset is being used to study how galaxy properties change with environment across cosmic time. (science.nasa.gov) Additional COSMOS-Web analyses are likely to keep appearing as teams work through the survey’s wide-area imaging and related measurements. (news.ucr.edu) (iopscience.iop.org)