Researchers find clever method to correct galaxy measurements

Pune: Researchers have devised a clever method to correct distance errors in galaxy measurements, making our maps of the universe and our understanding of dark matter and cosmic evolution much more accurate.Divya Rana of Leiden University and Surhud More of the Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune, recently published their findings in Physical Review, offering a breakthrough that promises more accurate distance measurements for galaxies across the cosmos.Their technique will play a crucial role in ensuring highly accurate redshift measurements, enabling reliable studies of dark energy and the universe's evolution during the upcoming astronomical surveys, including those by the Vera C Rubin Observatory, the Nancy Grace Roman Space Telescope, and the Euclid Mission.Astronomers, as per IUCAA, use the faint light from distant galaxies to understand the history and makeup of our universe. As light from these background galaxies travels toward Earth, it passes by closer foreground galaxies, and the gravity of the closer galaxies bends and distorts the light — a phenomenon called weak gravitational lensing.These distortions help scientists map matter—most of it invisible dark matter—and study how structures form across cosmic time. For this, scientists need to know exactly how much the light has stretched as it travelled, a concept known as redshift. The uncertainty in the redshift of the galaxy can result in a biased understanding of the cosmological parameters that describe the universe."We started our work in 2023. By comparing how matter around the same foreground galaxies bends light from background galaxies at different distances, we can cancel out complex astrophysical effects and isolate a clean measurement of the universe's geometry," explained More."Think of it as using a cosmic ruler to correct distance estimates. The most challenging part was running a large number of tests to ensure our results were robust," he added.Applying this approach to data from the Subaru Hyper Suprime-Cam (HSC) survey—a massive project mapping the distribution of matter across the sky—the researchers successfully corrected biases in redshift estimates. This, in turn, enabled them to derive more reliable cosmological parameters, including the density of matter in the universe and the amplitude of inhomogeneities, which measure variations between dense and less-dense regions.