Year: 2025
Type: article
Abstract: We report the spectroscopic confirmation of the background source of the most distant Einstein ring known to date, the COSMOS-Web ring. This system consists of a complete Einstein ring at z = 5.1, which is lensed by a massive early-type galaxy at z ∼ 2. The redshift z = 5.1043 ± 0.0004 is unambiguously identified with our NOEMA and Keck/MOSFIRE spectroscopy; the NOEMA observations reveal the CO(4–3) and CO(5–4) lines at > 8σ, and the MOSFIRE data detect [O II] at ∼6σ. Using multiwavelength photometry spanning near-infrared to radio bands, we find that the lensed galaxy is a dust-obscured starburst (M⋆ ∼ 1.8 × 1010 M⊙, SFRIR ∼ 60 M⊙ yr−1) with a high star formation efficiency (gas depletion time τdep < 100 Myr), as indicated by the [C I](1–0) non-detection. The redshift confirmation re-validates that the total lens mass budget within the Einstein radius is fully accounted for by the stellar and dark matter components, without the need of modifying the initial mass function or dark matter distribution profile. This work paves the way for detailed studies and future follow-ups of this unique lensing system, which is an ideal laboratory for studying mass distribution at z ∼ 2 and physical conditions of star formation at z ∼ 5.
Authors: Marko Shuntov, Shuowen Jin, Wilfried Mercier, Jeyhan S. Kartaltepe, Rebecca Larson, Ali Ahmad Khostovan, Raphaël Gavazzi, James W. Nightingale, Olivier Ilbert, Rafael Arango-Toro, Maximilien Franco, Hollis B. Akins, Caitlin M. Casey, Henry Joy McCracken, Laure Ciesla, Georgios E. Magdis, Aristeidis Amvrosiadis, Andrea Enia, Andreas L. Faisst, Anton M. Koekemoer, Clotilde Laigle, Damien Le Borgne, Richard Massey, Thibaud Moutard, Mattia Vaccari
Institutions: University of Copenhagen, DTU Space, Technical University of Denmark, Centre National de la Recherche Scientifique, Aix-Marseille Université, Rochester Institute of Technology, Institut d'Astrophysique de Paris, Sorbonne Université, Durham University, The University of Texas at Austin, Osservatorio di Astrofisica e Scienza dello Spazio, National Institute for Astrophysics, University of Bologna, California Institute of Technology, Infrared Processing and Analysis Center, Space Telescope Science Institute
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science Foundation, National Aeronautics and Space Administration, W. M. Keck Foundation, California Institute of Technology, Villum Fonden, NASA Exoplanet Science Institute, European Commission, National Research Foundation, Agence Nationale de la Recherche, Danmarks Grundforskningsfond, Centre National d’Etudes Spatiales, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, HORIZON EUROPE Framework Programme
OpenAlex ID: W6922008558
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