The DESI Single Fiber Lens Search. I. Four Thousand Spectroscopically Selected Galaxy–Galaxy Gravitational Lens Candidates

Journal Article · Tue Mar 03 00:00:00 EST 2026 · The Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/ae3f06· OSTI ID:3010182

Karp, Juliana S. M. ^[1]; Schlegel, David J.; Huang, Xiaosheng; Padmanabhan, Nikhil; Bolton, Adam S.; Storfer, Christopher J.; Aguilar, J.; Ahlen, S.; Bailey, S.; Bianchi, D.; Brooks, D.; Castander, F. J.; Claybaugh, T.; Cuceu, A.; de la Macorra, A.; Della Costa, J.; Doel, P.; Font-Ribera, A.; Forero-Romero, J. E.; Gaztañaga, E. ; Gontcho A Gontcho, S.; Gutierrez, G.; Honscheid, K.; Ishak, M.; Jimenez, J.; Joyce, R.; Juneau, S.; Kirkby, D.; Kremin, A.; Lamman, C.; Landriau, M.; Le Guillou, L.; Manera, M.; Martini, P.; Meisner, A.; Miquel, R.; Moustakas, J.; Nadathur, S.; Percival, W. J.; Poppett, C.; Prada, F.; Pérez-Ràfols, I.; Rossi, G.; Sanchez, E.; Schubnell, M.; Sprayberry, D.; Tarlé, G.; Weaver, B. A.; Zhou, R.

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1. Univ. of Washington, Seattle, WA (United States); Yale Univ., New Haven, CT (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States); DESI Collaboration. et al.

We present 4110 strong gravitational lens candidates, 3887 of which are new discoveries, selected from a sample of 5,837,154 luminous red galaxies (LRGs) observed with the Dark Energy Spectroscopic Instrument (DESI). Candidates are identified via the presence of background ionized oxygen [O II] nebular emission lines in the foreground LRG spectra, which may originate from the lensing of higher-redshift star-forming galaxies. Using the measured foreground redshift, background redshift, and integrated flux of the background [O II] doublet, we integrate over impact parameters to compute the probability that each candidate is a lens. We expect 53% of candidates to be true lenses with Einstein radii ranging from 0$$^{''}_.$$1–4", which can be confirmed with high-resolution imaging. Confirmed strong lenses from this sample will form a valuable cosmological data set, as strong gravitational lensing is the only method to directly measure dark matter halo substructure at cosmological distances. We independently recover the host of the multiply imaged gravitationally lensed type Ia supernova iPTF16geu. Monitoring these lenses for future multiply lensed transients will enable (a) H₀ measurements via time-delay cosmography and (b) substructure measurements via flux ratios.

• Research Organization: Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States)
• Sponsoring Organization: National Science Foundation (NSF); USDOE Office of Science (SC), High Energy Physics (HEP); USDOE Office of Science (SC), Workforce Development for Teachers and Scientists (WDTS)
• Grant/Contract Number: 89243024CSC000002; AC02-05CH11231; SC0017660
• Other Award/Contract Number: DGE-2140004; AST-095094
• OSTI ID: 3010182
• Report Number(s): FERMILAB-PUB--25-0946-PPD; oai:inspirehep.net:3093475; arXiv:2512.04275
• Journal Information: The Astrophysical Journal, Journal Name: The Astrophysical Journal Journal Issue: 2 Vol. 999; ISSN 0004-637X; ISSN 1538-4357
• Publisher: IOP Publishing
• Country of Publication: United States
• Language: English