Revolutionizing Hubble Constant Measurement: Pixelized Galaxy Cluster Strong Lens Modeling
A groundbreaking study led by the Shanghai Astronomical Observatory (SHAO) of the Chinese Academy of Sciences has unveiled a novel approach to enhance the precision of the Hubble constant (H0) measurement. For the first time, researchers have demonstrated that pixelized strong-lensing modeling on a galaxy cluster scale can significantly improve the accuracy of H0 inference, a key parameter describing the universe's expansion rate.
Published in the Monthly Notices of the Royal Astronomical Society, the research introduces a new technical pathway for determining cosmic distances through strongly lensed supernovae. The Hubble constant, a cornerstone of modern cosmology, has long been a subject of debate due to discrepancies between early and late universe measurements. This study offers a promising solution to bridge this gap.
Strongly lensed supernovae provide a unique opportunity to measure cosmic distances directly through time delays between multiple images, offering an independent H0 inference. However, current modeling limitations have hindered precision. The CURLING project's earlier work laid the foundation for the researchers' development of a pixelized strong lens modeling framework.
Comparing traditional point-source modeling with the pixelized method, the study revealed remarkable results. Pixelized modeling significantly reduced uncertainty to ±0.8 km/s/Mpc, an improvement of over tenfold. This breakthrough suggests that high-resolution observational data from telescopes like the James Webb Space Telescope (JWST) can enhance surface brightness information from arc-like systems, reducing systematic errors and making strongly lensed supernovae a high-precision cosmological tool.
Looking ahead, the researchers simulated future observations with upcoming survey facilities. Under the Rubin Observatory's Legacy Survey of Space and Time (LSST) conditions, time-delay measurements could achieve uncertainties of about 1.5%. The Chinese Survey Space Station Telescope—Multi-Channel Imager (CSST-MCI) further enhances precision. When combined with pixelized modeling, CSST-MCI observations could constrain H0 to within 0.1 km/s/Mpc.
The study emphasizes that lens-model uncertainties are now the primary limitation in H0 inference. The fusion of high-resolution imaging and pixelized strong-lensing modeling paves the way for percent-level precision in H0 measurements in the near future.
Dr. Xie Yushan, the study's first author, highlighted the significance of pixelized modeling, stating, 'It allows us to utilize all the information encoded in lensed arcs, moving us closer to precision cosmology with cluster-scale strong lensing.'
Prof. Shan Huanyuan, the corresponding author, added, 'With JWST, Euclid, and the upcoming Chinese Space Station Telescope, we are entering a golden era of strong-lensing research. This work demonstrates the potential for high-precision cosmological measurements once more lensed supernova samples are available.'
The research, titled 'CURLING – II. Improvement on the H0 inference from pixelized cluster strong lens modeling,' is published in the Monthly Notices of the Royal Astronomical Society (2025). The study's DOI is 10.1093/mnras/staf1740.
