Press Release: Euclid Quick Data Release 1

2025-03-19, Euclid Consortium

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Euclid Consortium: New science results and exclusive data from the Euclid space telescope

Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, E. Bertin, G. Anselmi

Today, the Euclid Consortium (EC) releases scientific papers and exclusive data based on observations made by the Euclid space telescope. Three different fields, corresponding to 63 square degrees in total, have been observed and analyzed by scientists of the Euclid Collaboration, demonstrating the unprecedented power of this telescope designed to provide the most precise map of our Universe over time. With just 0.45% of Euclid’s nominal survey, EC scientists have achieved a wealth of exciting scientific results. These include the discovery of strong gravitational lensing systems, the exploration of galaxy clusters and the cosmic web, the characterization of active galactic nuclei (AGN) and quasars, studies on galaxy evolution and morphology, and the identification of numerous dwarf galaxies and transients. Those results are described in a series of 27 scientific publications. In addition, the Consortium also publishes 7 technical papers that describe how this data has been processed by the Science ground segment experts, the team responsible for processing and analyzing the telescope’s data.

The Euclid Consortium

The Euclid Consortium, in partnership with the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA), has designed and built the instruments of the Euclid space telescope. It has also developed and currently operates the data pipeline, the system responsible for processing and organizing data from the telescope. This mission aims to map the extragalactic sky over a period of six years, providing unique data that offer new insights into dark energy and dark matter. Launched on July 1st, 2023, the telescope successfully began its cosmological survey on February 14th, 2024.

The Euclid Consortium comprises more than 2600 members, from more than 300 laboratories in 15 European countries, plus Canada, Japan, and the United States, covering various fields in astrophysics, cosmology, theoretical physics, and particle physics. After a first publication of early-release observations (ERO) results and data in May 2024, the Collaboration now presents a second set of Euclid observations and publications demonstrating further progress. This new data release, titled ‘Q1’, for ‘Quick Release 1’, is published today.

The Euclid Consortium gathered in Rome in June 2024. Credit : Marco Scodeggio

The ‘Q1’ data set

The data unveiled today provide a first glimpse of Euclid’s cosmological survey. These fields are illustrative of what will be extensively analysed by scientists within the Euclid collaboration to map the large-scale structure of the Universe across cosmic time, and investigate the nature of dark matter and dark energy in the years to come. With a sky area of about 63 square degrees, this release is seven times larger than the earlier ERO release, and represents the largest contiguous areas of sky ever observed with an optical/near-infrared space telescope. The Q1 data are complemented by observations of a star-forming region in our own galaxy, taken early-on in the mission to test and improve Euclid’s guiding performance.

Thanks to Euclid’s very wide field of view and high resolution, these exquisite data are also highly valuable for various astrophysical studies on smaller scales, ranging from clusters of galaxies to planet-sized objects. All the papers published today are dedicated to this non-cosmological science, also called legacy science.

Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre, E. Bertin, G. Anselmi

Scientific results

Euclid maps the Universe across cosmic time and traces the evolution of large-scale structures that form the so-called cosmic web. Using the Q1 fields, researchers have successfully recovered galaxy filaments and explored their role in galaxy morphology and alignment far beyond previous limits, as well as which properties and environments make galaxy clusters connect to these filaments. “For the first time, we are studying the cosmic web in a statistical way on a very large area.” says Simona Mei, Professor at Université Paris Cité (CNRS/IN2P3/APC). As key building blocks of the cosmic web, numerous previously unknown galaxy clusters have been discovered and characterized – some from the first ages of our Universe, many exhibiting strong gravitational lensing features.

The Euclid space mission has also ushered in a new era in the study of active galactic nuclei (AGN), which represent the bright phase of supermassive black holes at the center of nearly every galaxy. “These data help us better understand how black holes and their host galaxies grow together throughout cosmic history.” says Berta Margalef-Bentabol, Postdoctoral researcher at the Netherlands Institute for Space Research. Using advanced AI algorithms, researchers have established vast catalogs of AGN and red quasars – extremely luminous AGN – featuring thousands of new candidates with unprecedented positional measurements across a large area of the sky, and are now able to statistically confirm how galaxy mergers drive AGN activity.

Galaxy morphology and evolution are central to Euclid’s non-cosmological science. In August 2024, members of the Euclid Consortium launched a first citizen-science campaign on the Zooniverse platform, enlisting thousands of volunteers to train a deep-learning algorithm classifying galaxy morphologies. The resulting catalogue, based on the first 0.45% of the ~100 million lower-redshift galaxies that Euclid will ultimately capture in detail, has already proven valuable to researchers. Moreover, thanks to this large volume of high-quality data, scientists were able to observe differences with respect to simulated galaxy shapes and features. They also investigated how different environments, star-formation rates, and morphologies are linked and drive the evolution of galaxies in various epochs of our Universe.

Credit: ESA/Euclid/Euclid Consortium/NASA, image processing by M. Walmsley, M. Huertas-Company, J.-C. Cuillandre

A few months ago, the Euclid Collaboration launched another citizen-science campaign on the Zooniverse platform. With the help of over 1,000 participants and newly trained machine-learning algorithms, more than 500 strong gravitational lens candidates at galaxy scale were identified in the Q1 fields. “The resolution of the Euclid data allowed us to see these lensed systems in incredible detail, and these data are only a small fraction of the lenses we hope to find in the coming years as the survey continues,” says Philip Holloway, PhD student at the University of Oxford. These rare phenomena, predicted by Einstein’s general relativity, are invaluable tools for understanding the distribution of dark matter around galaxies, studying internal dynamics in galaxy clusters, and even uncovering previously hidden galaxies. So far, only about 150 of these lenses had been observed by space telescopes.

Thanks to Euclid’s vast field of view and its ability to detect faint and distant objects, researchers have further identified thousands of new dwarf galaxy candidates, as well as thousands of mysterious ‘little red dot’ candidates – objects from the early Universe first observed a few years ago with JWST. Euclid has also allowed for the determination of host galaxies for several previously hostless transient bright sources, and the physical properties of dusty, massive red galaxies from the early Universe, demonstrating again Euclid’s capability to deliver highly valuable data across a wide range of objects and cosmic ages.

All these results are described in a series of papers, which have all been subject to the internal peer review process. They are available at Euclid Consortium Publications (and as part of this PR) and will appear as pre-publications on the ArXiv later today. The images and science-ready catalogues are available for download from ESA.

Processing papers

While the scientific analyses presented above are unprecedented and highly promising for the future of the mission, they represent only a small fraction of the extensive work carried out by the Euclid Consortium. Producing high-quality data – first for Euclid Consortium researchers and later for the international scientific community – requires an extensive processing effort. Once captured by the telescope, raw images undergo rigorous treatment by the engineers and researchers of the Euclid science ground segment (SGS), who work daily to transform them into usable data, paving the way to more advanced scientific analyses and discoveries. “The quality of Euclid data is incredibly high. The SGS is already preparing the next release, using increasingly complex algorithms.” explains Andrea Zacchei, Senior Astronomer at the Trieste Astronomical Observatory (INAF/OATs) and Project Manager of the SGS.

These multi-faceted data-processing algorithms correct the VIS (optical) and NISP (infrared) camera data for numerous instrumental and systematic effects. They extract tens of millions of sources from their images, determine their precise brightness and position on the sky, and in combination with ground-based observations at other wavelengths estimate their redshift, which gives their distances. For some sources, this redshift is precisely determined from their spectra given by the NISP instrument. All these procedures require numerous and complex algorithms to meet Euclid’s rigorous quality control standards. The entirety of this processing is described in the seven technical papers published today.

Future milestones of the Euclid mission

The next data release from the Euclid Consortium will concern Euclid’s nominal survey and core-science, including results about the nature of dark energy. A first worldwide data release is currently planned for October 2026. At least two other quick releases and two other data releases are expected before 2031, the currently foreseen end date of Euclid’s main survey.

ESA Q1 release webstory

Find ESA’s story here:
https://www.esa.int/Science_Exploration/Space_Science/Euclid/Euclid_opens_data_treasure_trove_offers_glimpse_of_deep_fields

Press inquiries

For more information, or press inquiries to the Euclid Consortium, please email menard@iap.fr.

Euclid Consortortium Press Contacts page includes national contacts

Euclid Q1 overview, data products and processing:

Scientific results using Euclid Q1 data:

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