TDCOSMO

XVI. Measurement of the Hubble constant from the lensed quasar WGD 2038–4008

¹ Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
² European Southern Observatory, Alonso de Córdova 3107, Vitacura, Santiago, Chile
³ Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny, 1290 Versoix, Switzerland
⁴ Department of Astronomy & Astrophysics, University of Chicago, Chicago, IL 60637, USA
⁵ Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL 60637, USA
⁶ Technical University of Munich, TUM School of Natural Sciences, Physics Department, James-Franck-Straße 1, 85748 Garching, Germany
⁷ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
⁸ Academia Sinica Institute of Astronomy and Astrophysics (ASIAA), 11F of ASMAB, No. 1, Section 4, Roosevelt Road, Taipei 106216, Taiwan
⁹ Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics, Stanford University, Stanford, CA, USA
¹⁰ Department of Physics and Astronomy, University of California, Davis, CA 95616, USA
¹¹ STFC Hartree Centre, Sci-Tech Daresbury, Keckwick Lane, Daresbury, Warrington WA4 4AD, UK
¹² Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
¹³ Fermi National Accelerator Laboratory, PO Box 500 Batavia, IL 60510, USA
¹⁴ ICC-UB Institut de Ciències del Cosmos, University of Barcelona, Martí Franquès, 1, E-08028 Barcelona, Spain
¹⁵ ICREA, Pg. Lluís Companys 23, Barcelona E-08010, Spain
¹⁶ SLAC National Accelerator Laboratory, Menlo Park, CA, USA
¹⁷ Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy
¹⁸ INAF – IASF Milano, Via A. Corti 12, I-20133 Milano, Italy
¹⁹ STAR Institute, Quartier Agora, Allée du Six Aout, 19c, B-400 Liège, Belgium
²⁰ Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095, USA

Received: 4 June 2024
Accepted: 4 July 2024

Abstract

Time-delay cosmography is a powerful technique to constrain cosmological parameters, particularly the Hubble constant (H₀). The TDCOSMO Collaboration is performing an ongoing analysis of lensed quasars to constrain cosmology using this method. In this work, we obtain constraints from the lensed quasar WGD 2038−4008 using new time-delay measurements and previous mass models by TDCOSMO. This is the first TDCOSMO lens to incorporate multiple lens modeling codes and the full time-delay covariance matrix into the cosmological inference. The models are fixed before the time delay is measured, and the analysis is performed blinded with respect to the cosmological parameters to prevent unconscious experimenter bias. We obtain D_{Δ t} = 1.68_−0.38^+0.40 Gpc using two families of mass models, a power-law describing the total mass distribution, and a composite model of baryons and dark matter, although the composite model is disfavored due to kinematics constraints. In a flat ΛCDM cosmology, we constrain the Hubble constant to be H₀ = 65₋₁₄⁺²³ km s⁻¹ Mpc⁻¹. The dominant source of uncertainty comes from the time delays, due to the low variability of the quasar. Future long-term monitoring, especially in the era of the Vera C. Rubin Observatory’s Legacy Survey of Space and Time, could catch stronger quasar variability and further reduce the uncertainties. This system will be incorporated into an upcoming hierarchical analysis of the entire TDCOSMO sample, and improved time delays and spatially-resolved stellar kinematics could strengthen the constraints from this system in the future.