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Published: 13th October, 2025, Academia Sinica, Institute of Astronomy & Astrophysics (ASIAA), Taiwan
Utilizing the James Clerk Maxwell Telescope (JCMT) in Hawaii and the James Webb Space Telescope (JWST), an international team led by undergraduate student Ting-Kai Yang and Dr. Chian-Chou Chen from the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA) has confirmed 13 new strongly lensed, faint dusty galaxies, which are nearly an order of magnitude fainter than previously known lensed sources.. The result has published in the Astrophysical Journal Letters in September, 2025.
Gravitational lensing is one of the most striking predictions of Einstein’s general relativity. In the case of strong lensing—when a background galaxy is magnified by more than a factor of two—this effect occurs if a distant galaxy aligns closely with a foreground galaxy along our line of sight. The frequency of such alignments reflects the distribution of galaxies across the cosmos, making strong lensing a powerful tool to probe the Universe’s mass distribution.
Now, an international team led by ASIAA and National Taiwan University (NTU) has unveiled a previously underexplored population of faint, dusty star-forming galaxies whose emission is strongly magnified by intervening galaxies acting as cosmic lenses. This breakthrough enables the study of galaxies that would otherwise be too dim to detect, opening a new window on how galaxies formed and evolved in the early Universe.
“We anticipated that many faint, dusty galaxies remain hidden to current instruments, but confirming them via strong lensing has been a major challenge,” said Ting-Kai Yang, an undergraduate student at NTU and the lead author of this study.
The team combined deep submillimeter data from the SCUBA-2 camera on JCMT in Maunakea with the unparalleled imaging capabilities of JWST. This effort led to the confirmation of 13 new strongly lensed, faint dusty galaxies. Thanks to JCMT’s uniform survey, the team was able to measure for the first time that about 1% of these dusty submillimeter galaxies at this flux level are strongly lensed, in line with theoretical predictions.
“With the unprecedented depth reached by the SCUBA-2 survey and the leverage of JWST’s imaging capabilities, we are finally revealing these ‘hidden gems’ that help test galaxy evolution models more rigorously,” said Wei-Hao Wang, leader of the SCUBA-2 survey and deputy director of ASIAA.
This discovery pushes the limits of sensitivity for lensing studies and provides fresh insights into how matter—both visible and dark—is distributed across the Universe. “We expect many more such systems will be discovered from the Euclid space telescope as well as the upcoming Roman space telescope. Our study marks the first step into a previously inaccessible regime,” said Chian-Chou Chen, an associate research fellow at ASIAA and a visiting scientist at the JCMT.
This gallery of JWST images highlights six striking examples of strongly lensed dusty galaxies discovered by the team. In each panel, the bright central object is a foreground galaxy. The redder, arc- or ring-shaped features nearby are more distant dusty galaxies whose light has been magnified and distorted by the gravity of the foreground galaxy Image Credit: JWST/Chian-Chou Chen
More Information:
This research presented in a paper "Unveiling a Population of Strong Galaxy–Galaxy Lensed, Faint Dusty Star-forming Galaxies,” by Yang et al. has appeared in the Astrophysical Journal Letters on Spetember 1st, 2025.
Media Contact:
Dr. Chian-Chou Chen, Email: ccchen@asiaa.sinica.edu.tw, Tel: +886 2 2366 5447
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