Oral Presentation

Where Clusters Collide and Cosmic Filaments Connect: Weak Lensing with Subaru and Rubin

Author(s): Hyejeon Cho (Yonsei University)

Presenter: Hyejeon Cho (Yonsei University)

Galaxy clusters grow at the intersections of cosmic filaments through mergers and the continuous accretion of matter. These processes are expected, based on theoretical models, to influence the properties of gas and galaxies in and around clusters, leaving behind distinct dark matter structures that channel baryonic flows. While previous studies have hinted at the presence of such structures, direct detection through weak lensing (WL) has remained elusive, hindered by systematic uncertainties and low signal-to-noise ratios. Using wide-field data from the Subaru Hyper Suprime-Cam, we perform WL analyses to precisely map dark matter distributions in merging clusters and their surrounding large-scale structures, carefully addressing various sources of systematics. We successfully detect intracluster filaments connected to the cosmic web, as previously suggested by galaxy distributions. In addition, we uncover low-contrast mass bridges in several merging clusters, providing direct evidence of past collisions. We also find that in many merging clusters, the merger axes are strongly aligned with the large-scale distributions of cluster member galaxies. By combining these WL results with multi-wavelength observations, we gain deeper insights into merger scenarios, gas physics, and the growth of structure, offering new observational constraints on the nature of dark matter. I will also provide a brief overview of Rubin/LSST, highlighting early WL results from the LSSTComCam campaign. These preliminary results demonstrate the potential of the WL capabilities of Rubin and illustrate the prospects for mapping dark matter and large-scale structures with the upcoming survey.