An international team of scientists led by the Institute of Cosmos Sciences of the University of Barcelona and the Institute of Space Studies of Catalonia (ICCUB-IEEC) have introduced REGALADE, an unprecedented all-sky catalog that brings together nearly 80 million galaxies. This achievement, now published in the prestigious journal Astronomy & Astrophysics (A&A), marks a turning point for astronomy, enabling researchers to explore cosmic events with a level of precision never seen before.
When a telescope detects a sudden phenomenon such as a supernova or the merger of two black holes or neutron stars, astronomers need to know where to look and how far away the event occurred. That requires identifying the galaxy hosting the event. Until now, existing catalogs were incomplete beyond about 300 million light-years, leaving large gaps in our map of the nearby Universe. REGALADE fills those gaps by combining data from major surveys and cleaning it using data from the Gaia mission to remove stars mistakenly classified as galaxies. The result is a high-purity, high-completeness catalog that includes accurate distances and size measurements for all galaxies, and stellar masses for most.
“REGALADE began as a user experience problem: astronomers relied on many popular catalogs, but each one covered only part of the sky or lacked key information,” explains Hugo Tranin, ICCUB researcher and lead author of the study. “By merging data from 14 widely used catalogs and deep imaging surveys, we now have a single, unified place to look for galaxy distances and properties. This drastically simplifies the daily work of astronomers and allows our team to retrieve distances for more than 75% of the transients reported worldwide every day.” The team has also released an interactive sky viewer (https://blackpearl.blackgem.org/regalade.php), where the public can explore the REGALADE catalog and navigate millions of galaxies in just a few clicks.
The scale and depth of REGALADE are extraordinary. It covers the entire sky and reaches out to more than four billion light-years, mapping about 10% of the volume of the observable Universe. This completeness means astronomers can now identify many more host galaxies for all types of cosmic events, from infrared to X-rays, and significantly improve strategies for gravitational-wave follow-up. According to Nadia Blagorodnova, ICCUB-IEEC researcher and co-author, “Observatories like the Vera Rubin Observatory will detect millions of cosmic events every night. REGALADE ensures we can identify their host galaxies quickly and accurately, enabling rapid classification of rare transients such as luminous red novae, stellar mergers that our team actively studies, and opening the door to the discovery of entirely new types of celestial phenomena.”
The study was led by Hugo Tranin, researcher at the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), with the participation of ICCUB-IEEC researchers Nadejda Blagorodnova, Marco A. Gómez-Muñoz and Maxime Wavasseur. Their work combines expertise in time-domain astronomy, galaxy surveys and multi-messenger astrophysics, positioning the ICCUB team at the forefront of efforts to build comprehensive resources for the next generation of observatories.
Reference:
Tranin, H., Blagorodnova, N., Gómez‑Muñoz, M. A., Wavasseur, M., Groot, P. J., Landsberg, L., Stoppa, F., Bloemen, S., Vreeswijk, P. M., Pieterse, D. L. A., van Roestel, J., Scaringi, S., Faris, S.,et al. (2025). A catalog to unite them all: REGALADE, a revised galaxy compilation for the advanced detector era. [Article]. Astronomy & Astrophysics. https://doi.org/10.1051/0004-6361/202556896
