Gaia GraL: The GraL catalogue of gravitationally lensed quasars

X. Matched with Gaia data, redshifts, and time delays

¹ Laboratoire d’Astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
² Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão, 1226, Cidade Universitária, 05508-900 São Paulo, SP, Brazil
³ Donald Bren School of Information and Computer Sciences, University of California, Irvine, CA 92697, USA
⁴ CENTRA/SIM, Faculdade de Ciéncias, Universidade de Lisboa, Ed. C8, Campo Grande, 1749-016, Lisboa, Portugal
⁵ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France
⁶ Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia
⁷ Center for Astrophysics Harvard & Smithsonian, 60 Garden St., 02138 Cambridge, MA, USA
⁸ Space sciences, Technologies and Astrophysics Research (STAR) Institute, University of Liège, Belgium
⁹ Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria, Australia
¹⁰ Center for Theoretical Physics, Polish Academy of Sciences, Warsaw, Poland
¹¹ Lohrmann-Observatorium, Technische Universitaet Dresden, 01062 Dresden, Germany
¹² Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital 263002, India
¹³ Departamento de Física CCET, Universidade Federal de Sergipe, Rod. Marechal Rondon s/n, 49.100-000 Jardim Rosa Elze, São Cristóvão, SE, Brazil
¹⁴ Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, AL10 9AB, UK
¹⁵ Astronomisches Rechen-Institut (ARI), Zentrum fur Astronomie der Universitaet Heidelberg (ZAH), Moenchhofstr. 12–14, 69120 Heidelberg, Germany
¹⁶ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00078 Monte Porzio Catone, Italy
¹⁷ Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, China

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 10 November 2025
Accepted: 18 February 2026

Abstract

Determining the Hubble constant tension requires alternative strategies, and multiply imaged quasars, with their intermediate redshifts, can potentially be used in this regard. We provide a currently complete catalogue of spectroscopically confirmed lensed quasars with ESA/Gaia astrometry and photometry, as well as redshifts and time delays when available. In addition to the improved astrometry, the catalogue increases the number of lensed quasars by a factor of 1.5 (now 364, of which 277 are doubles and 87 are quads or triples) and significantly increases the number of lensing galaxies detected (now 218), which represents a major step forward. Redshifts are provided for 347 quasars and 188 deflectors. A completely new table of time delays, required for estimates of H₀, is presented, with 195 time delays from 73 systems. Gaia absolute astrometry is sub-milliarcsecond and covers the entire sky. Future Gaia data releases will provide long-term photometry, which should provide many more time delays. The catalogues as presented here enable machine-learning techniques to be trained and tested and subsequently applied to the Gaia data releases. Finally, we derive simple but homogeneous models of the 18 quadruply imaged quasars for which images of all four components are presented in Gaia DR3.