Research Highlight

Scientists Unveil Technique to Measure Elusive Distances to Dark Matter Haloes

 Professor Kaiki Inoue from the Cosmology Laboratory at Kindai developed a novel method to measure distances to dark halos using gravitational lensing effects, with the results published on January 24, 2025, in the Journal of Cosmology and Astroparticle Physics (JCAP).

Research Background: Current cold dark matter models are uncertain at scales smaller than 1 Mpc, and while gravitational lens observations of quasars and galaxies are revealing small-scale structures like dwarf galaxies, these dark halos are extremely difficult to detect optically.

Research Methodology: The researchers developed a novel approach using a "primary lens + secondary lens" gravitational lensing system, theoretically formulating and analyzing the characteristic "B-mode" pattern of gravitational lensing effects, which had not been previously investigated in this context.

Key Findings: The study revealed that the B-mode amplitude is approximately one-third of the E-mode amplitude, and developed a method to estimate line-of-sight distances to dark halos by observing B-mode characteristics, while also identifying how mass sheet degeneracy affects distance measurements.

Research Impact: This research provides a principled approach to measuring line-of-sight distances to optically invisible dark halos, with the potential to resolve uncertainties in small-scale dark matter distribution by using time delay measurements to address mass sheet degeneracy.

 

Author: Kaiki Taro Inoue

Title: Measuring Line-of-sight Distances to Haloes with Astrometric Lensing  B-mode

Journal Name: Journal of Cosmology and Astroparticle Physics

Impact Factor: 5.3 (2023)

Publication date Jan.24, 2025

The preprint is available in ArXiv.