TDCOSMO 2025: Cosmological constraints from strong lensing time delays

¹ Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
² Fermi National Accelerator Laboratory, PO Box 500 Batavia, IL 60510, USA
³ Department of Astronomy & Astrophysics, University of Chicago, Chicago, IL 60637, USA
⁴ Sub-Department of Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
⁵ Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
⁶ Institució Catalana de Recerca i Estudis Avançats (ICREA), Passeig de Lluís Companys 23, 08010 Barcelona, Spain
⁷ European Southern Observatory, Alonso de Córdova, 3107 Vitacura, Santiago, Chile
⁸ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
⁹ Department of Physics and Astronomy, UC Davis, 1 Shields Ave., Davis, CA 95616, USA
¹⁰ Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
¹¹ SLAC National Laboratory, 2575 Sand Hill Rd, Menlo Park, CA, 94025
¹² Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Straße 1, 85748 Garching, Germany
¹³ Technical University of Munich, TUM School of Natural Sciences, Physics Department, James-Franck-Straße 1 85748, Garching
¹⁴ Department of Physics and Astronomy, University of California, Los Angeles, CA 90095, USA
¹⁵ DARK, Niels Bohr Institute, University of Copenhagen, Jagtvej 155A, 2200 Copenhagen, Denmark
¹⁶ Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland
¹⁷ IPAC, California Institute of Technology, MC 314-6, 1200 E. California Boulevard, Pasadena, CA 91125, USA
¹⁸ Instituto de Física y Astronomía, Universidad de Valparaíso, Avda. Gran Bretaña 1111, Valparaíso, Chile
¹⁹ Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
²⁰ Center for Astronomy, Space Science and Astrophysics, Independent University, Bangladesh, Dhaka 1229, Bangladesh
²¹ STAR Institute, Liège Université, Quartier Agora – Allée du six Août, 19c B-4000 Liège, Belgium
²² Department of Astronomy, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
²³ Shanghai Key Laboratory for Particle Physics and Cosmology, Shanghai Jiao Tong University, Shanghai 200240, China
²⁴ Key Laboratory for Particle Physics, Astrophysics and Cosmology, Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240, China
²⁵ Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218, USA
²⁶ HEP Division, Argonne National Laboratory, Lemont, IL 60439, USA

^⋆ Corresponding authors: simon.birrer@stonybrook.edu, mmillon@ethz.ch, ajshajib@uchicago.edu

Received: 4 June 2025
Accepted: 28 September 2025

Abstract

We present cosmological constraints from eight strongly lensed quasars (hereafter, the TDCOSMO-2025 sample). Building on previous work, our analysis incorporated new deflector stellar velocity dispersions measured from spectra obtained with the James Webb Space Telescope (JWST), the Keck Telescopes, and the Very Large Telescope (VLT), utilizing improved methods. We used integrated JWST stellar kinematics for five lenses, VLT-MUSE for 2, and resolved kinematics from Keck and JWST for RX J1131−1231. We also considered two samples of non-time-delay lenses: 11 from the Sloan Lens ACS (SLACS) sample with Keck-KCWI resolved kinematics; and four from the Strong Lenses in the Legacy Survey (SL2S) sample. We improved our analysis of line-of-sight effects, the surface brightness profile of the lens galaxies, and orbital anisotropy, and corrected for projection effects in the dynamics. Our uncertainties are maximally conservative by accounting for the mass-sheet degeneracy in the deflectors’ mass density profiles. The analysis was blinded to prevent experimenter bias. Our primary result is based on the TDCOSMO-2025 sample, in combination with Ω_m constraints from the Pantheon+ Type Ia supernovae (SN) dataset. In the flat Λ cold dark matter (CDM), we find H₀ = 71.6^+3.9_−3.3 km s⁻¹ Mpc⁻¹. The SLACS and SL2S samples are in excellent agreement with the TDCOSMO-2025 sample, improving the precision on H₀ in flat ΛCDM to 4.6%. Using the Dark Energy Survey SN Year-5 dataset (DES-SN5YR) or DESI-DR2 baryonic acoustic oscillations (BAO) likelihoods instead of Pantheon+ yields very similar results. We also present constraints in the open ΛCDM, wCDM, w₀w_aCDM, and w_ϕCDM cosmologies. The TDCOSMO H₀ inference is robust and consistent across all presented cosmological models, and our cosmological constraints in them agree with those from the BAO and SN.