COSMOS-Web unveils deep universe map

The COSMOS-Web team has released the largest contiguous view of the deep universe ever captured by the James Webb Space Telescope (JWST), unveiling an unprecedented catalog of nearly 800,000 galaxies now available to the global scientific community. As the most expansive General Observer program of JWST’s Cycle 1, COSMOS-Web represents a monumental step forward in humanity’s quest to understand the early universe.

COSMOS-Web unveils deep universe map

Led by Dr. Jeyhan Kartaltepe of the Rochester Institute of Technology and Dr. Caitlin Casey of the University of California, Santa Barbara, COSMOS-Web surveyed 0.54 square degrees of the sky using JWST’s Near Infrared Camera (NIRCam) and 0.2 square degrees with the Mid Infrared Instrument (MIRI). The effort produced deep infrared imaging accompanied by a comprehensive catalog dubbed “COSMOS2025,” providing photometry, redshifts, structural measurements, and physical parameters of galaxies spanning nearly 98% of cosmic history.

"The sensitivity of JWST allows us to see fainter, more distant galaxies than ever before. We’re able to observe the universe’s earliest galaxies and study them in extraordinary detail. The quality of the data has far exceeded expectations," said Dr. Kartaltepe.

"Our aim was to construct a deep field image at a physical scale far beyond what had previously been attempted. COSMOS-Web has captured some of the rarest cosmic objects ever observed, and now this treasure trove of data is available to the entire scientific community," added Dr. Casey.

The program’s data release includes not only the NIRCam and MIRI imaging but also an interactive viewer that allows users to search for and explore individual galaxies. This user-friendly tool democratizes access to some of the most scientifically valuable data in astronomy.

The COSMOS2025 catalog, developed under the leadership of Dr. Marko Shuntov of the Cosmic DAWN Center, stands out for its precision and scope. The project required the development of novel tools to measure the photometry and morphology of galaxies across 37 images.

"This was a massive collaboration, and the result is one of the highest-quality galaxy datasets available. It opens the door to truly groundbreaking science," said Dr. Shuntov.

The team emphasized the importance of accessibility in scientific discovery. While the raw JWST data were made public immediately, they required significant processing, including artifact removal, background subtraction, and astrometric corrections. With the COSMOS2025 catalog, much of that processing is already done, providing researchers worldwide with ready-to-use data for scientific analysis.

"A major goal of COSMOS-Web is to make cutting-edge data accessible beyond the initial research team. By doing so, we accelerate discovery across the community,"  said Dr. Casey.

MIRI layout of the COSMOS field with a few example galaxies highlighted, showing a comparison between JWST/MIRI and Spitzer/IRAC at the same wavelength

The scale of COSMOS-Web’s contribution is also evident in the technical achievement of combining over 10,000 NIRCam images to produce the most extensive contiguous deep field from JWST to date.

"It was amazing to witness galaxies appearing on our screens that had previously been invisible," noted Dr. Maximilien Franco, lead author of the NIRCam data release paper and postdoctoral researcher at Université Paris-Saclay.

The MIRI instrument, operating at longer wavelengths less affected by cosmic dust, was equally vital in detecting early-universe galaxies and understanding their masses and star formation histories.

"With MIRI, we’re entering a new era in mid-infrared astronomy. The resolution and sensitivity are far beyond what Spitzer could achieve, and the COSMOS-Web data are a testament to that leap forward," said Dr. Santosh Harish, postdoctoral researcher at Rochester Institute of Technology.

Group photo at the COSMOS team meeting in Marseille, France, May 19-23, 2025

The COSMOS-Web team also unveiled two new studies highlighting the survey’s scientific reach. One study traces the structural evolution of the brightest group galaxies across 11 billion years, while another applies AI techniques to estimate key galactic properties directly from photometry.

"We can now use AI to predict galaxy evolution and understand how morphology and star formation are influenced by cosmic environments," said Dr. Ghassem Gozaliasl of Aalto University.

Processing of the COSMOS-Web dataset was carried out at the Institut d’Astrophysique de Paris with support from the Île-de-France region, CNES, and CNRS. The effort marks the latest milestone for The Cosmic Evolution Survey (COSMOS), a two-decade-old collaboration involving more than 200 scientists worldwide.

COSMOS-Web was designed to address three central scientific goals:

• Probe the Reionization Era, the universe’s first billion years after the Big Bang
• Track massive galaxy formation in the first two billion years
• Explore the relationship between dark matter and luminous matter in galactic structures
   

After more than 250 hours of observation across 150 visits, COSMOS-Web has succeeded in laying the groundwork for the next generation of astronomical discovery.

"We’ve created data and tools that will serve as the standard for future surveys. With JWST, we’re not just peering deeper into space, we’re transforming how we explore the universe," concluded Dr. Kartaltepe.

View the full press release