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arXiv · 2505.16158

Confirming HSC strong lens candidates with DESI Spectroscopy. I. Project overview and first results

Yiping Shu·Shen Li
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Abstract

Accurate redshift determinations of both lenses and sources are critical for confirming strong-lens systems and fully realizing their scientific value. However, the thousands of strong-lens candidates now routinely discovered in wide-field imaging surveys make one-by-one follow-up observations impractical. In this work, we investigate the capability and efficiency of large-scale spectroscopic surveys in confirming strong-lens systems. As a case study, we cross-match strong lens candidates identified from the Hyper Suprime-Cam Subaru Strategic Program with Data Release 1 (DR1) of the Dark Energy Spectroscopic Instrument (DESI). We find that DESI DR1 serendipitously observed putative lenses and/or lensed images in approximately 50\% of these candidates. Analyzing the DESI spectra for $\approx 500$ matched candidates that meet our selection criteria, we determine both lens and source redshifts for 27 systems. Additionally, 76 candidate systems feature lensing galaxies at $z > 0.8$, and one candidate system contains a quasar within its lensing galaxy. Applying this approach to other strong-lens candidates will yield many more confirmations, with a further several-fold increase anticipated from the final DESI data release. Our results highlight the growing importance of large-scale spectroscopic surveys in advancing strong lensing discoveries and science.

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Yiping Shu, Shen Li. 2025-05-22. Confirming HSC strong lens candidates with DESI Spectroscopy. I. Project overview and first results. https://doi.org/10.1007/s11433-025-2747-4

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