Title: A Million-Solar-Mass Object Detected at a Cosmological Distance Using Gravitational Imaging

Speaker: Wang Huihui（PMO）

Time: 12:15am, November 14, 2025

Location: 3-302, PMO Xianlin Campus

Abstract: Structure on subgalactic scales provides important tests of galaxy formation models and the nature of dark matter. However, such objects are typically too faint to provide robust mass constraints.  Here an extremely low-mass object is detected by means of its gravitational perturbation to a thin lensed arc observed with milli-arcsecond-resolution very long baseline interferometry. This is the lowest-mass object known to us, by two orders of magnitude, to be detected at a cosmological distance by its gravitational effect.