TDCOSMO

We present new time delays, the main ingredient of time delay cosmography, for 22 lensed quasars resulting from high-cadence r -band monitoring on the 2.6 m ESO VLT Survey Telescope and Max-Planck-Gesellschaft 2.2 m telescope. Each lensed quasar was typically monitored for one to four seasons, often shared between the two telescopes to mitigate the interruptions forced by the COVID-19 pandemic. The sample of targets consists of 19 quadruply and 3 doubly imaged quasars, which received a total of 1918 hours of on-sky time split into 21 581 wide-field frames, each 320 seconds long. In a given field, the 5- σ depth of the combined exposures typically reaches the 27 th magnitude, while that of single visits is 24.5 mag – similar to the expected depth of the upcoming Vera-Rubin LSST. The fluxes of the different lensed images of the targets were reliably de-blended, providing not only light curves with photometric precision down to the photon noise limit, but also high-resolution models of the targets whose features and astrometry were systematically confirmed in Hubble Space Telescope imaging. This was made possible thanks to a new photometric pipeline, lightcurver , and the forward modelling method STARRED . Finally, the time delays between pairs of curves and their uncertainties were estimated, taking into account the degeneracy due to microlensing, and for the first time the full covariance matrices of the delay pairs are provided. Of note, this survey, with 13 square degrees, has applications beyond that of time delays, such as the study of the structure function of the multiple high-redshift quasars present in the footprint at a new high in terms of both depth and frequency. The reduced images will be available through the European Southern Observatory Science Portal.

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Publication Details

Journal
Astronomy and Astrophysics
Published
2025-04-08
DOI
https://doi.org/10.1051/0004-6361/202553807
Citations
5
Primary Topic
Astronomy and Astrophysical Research
Type
article
Field-Weighted Citation Impact
5.96

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TDCOSMO

M. Rabus, R. G. McMahon, D. Sluse, Matthew W. Auger et al.
5 citations
Astronomy and Astrophysics
Astronomy and Astrophysical Research
5.96
article

TDCOSMO

M. Rabus, R. G. McMahon, D. Sluse, Matthew W. Auger, C. D. Fassnacht, F. Courbin, J. H. H. Chan, Paul Eigenthaler, Martin Millon, M. Hempel, V. Bonvin, M. Chijani, Fernando Bastos De Avila, S. Birrer, S. Kim, A. Hempel, Frédéric Dux, Alejandra Melo, S. H. Suyu, V. Motta, E. Paic, R. Lachaume, C. Lemon, Adriano Agnello, T. Anguita, A. Galan, F. Neira, E. Buckley‐Geer, T. Treu, K. Rojas, J. Frieman, P. J. Marshall
article en
5 citations

Abstract

We present new time delays, the main ingredient of time delay cosmography, for 22 lensed quasars resulting from high-cadence r -band monitoring on the 2.6 m ESO VLT Survey Telescope and Max-Planck-Gesellschaft 2.2 m telescope. Each lensed quasar was typically monitored for one to four seasons, often shared between the two telescopes to mitigate the interruptions forced by the COVID-19 pandemic. The sample of targets consists of 19 quadruply and 3 doubly imaged quasars, which received a total of 1918 hours of on-sky time split into 21 581 wide-field frames, each 320 seconds long. In a given field, the 5- σ depth of the combined exposures typically reaches the 27 th magnitude, while that of single visits is 24.5 mag – similar to the expected depth of the upcoming Vera-Rubin LSST. The fluxes of the different lensed images of the targets were reliably de-blended, providing not only light curves with photometric precision down to the photon noise limit, but also high-resolution models of the targets whose features and astrometry were systematically confirmed in Hubble Space Telescope imaging. This was made possible thanks to a new photometric pipeline, lightcurver , and the forward modelling method STARRED . Finally, the time delays between pairs of curves and their uncertainties were estimated, taking into account the degeneracy due to microlensing, and for the first time the full covariance matrices of the delay pairs are provided. Of note, this survey, with 13 square degrees, has applications beyond that of time delays, such as the study of the structure function of the multiple high-redshift quasars present in the footprint at a new high in terms of both depth and frequency. The reduced images will be available through the European Southern Observatory Science Portal.

Astronomy and AstrophysicsVol. 697
Institució Catalana de Recerca i Estudis Avançats (ES), Institute of Astronomy and Astrophysics, Academia Sinica (TW), Fermi National Accelerator Laboratory (US), University of Talca (CL), University of Liège (BE), Lehman College (US), Pontificia Universidad Católica de Chile (CL), Universidad Católica Andrés Bello (VE), ETH Zurich (CH), Universidad Católica de la Santísima Concepción (CL), Max Planck Institute for Medical Research (DE), Kavli Institute for Particle Astrophysics and Cosmology (US), Bridge University (SS), Museum of Military Medicine (GB), Menlo School (US), Sci-Tech Daresbury (GB), Max Planck Institute for Astrophysics (DE), Institut Català de Ciències del Clima (ES), Universidad Andrés Bello (CL), Max Planck Institute for Astronomy (DE), Max Planck Institute of Quantum Optics (DE), Institut Cartogràfic i Geològic de Catalunya (ES), European Southern Observatory (CL), Max Planck Computing and Data Facility (DE), Las Campanas Observatory (CL), Abiola Ajimobi Technical University Ibadan (NG), Cosmos Corporation (United States) (US), Stony Brook University (US), University of Portsmouth (GB), University of California, Davis (US), Netherlands Institute for Radio Astronomy (NL)
National Science Foundation, U.S. Department of Energy, European Space Agency, European Commission, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, China Scholarship Council, European Southern Observatory, Universidad Católica de la Santísima Concepción, Agencia Nacional de Investigación y Desarrollo, Max-Planck-Institut für Astronomie, University of California, Davis, HORIZON EUROPE Framework Programme, European Research Council
Openalex Percentile: Top 4%
Astronomy and Astrophysical Research
5.96
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