Oral Presentation

Weak-Lensing Mass Bias in Merging Galaxy Clusters

Author(s): Wonki Lee (Yonsei, CfA); Sangjun Cha (Yonsei); M. James Jee (Yonsei, UC Davis); Daisuke Nagai (Yale); Lindsay King (UT Dallas); John ZuHone (CfA); Urmila Chadayammuri (CfA); Sharon Felix (UT Dallas); Kyle Finner (IPAC)

Presenter: Wonki Lee (Yonsei University)

The mass of galaxy clusters provides a direct probe of cosmology. Weak gravitational lensing offers a powerful tool for estimating cluster masses without relying on assumptions about the cluster's dynamic state. In this study, we investigate potential biases in weak-lensing mass estimates during cluster mergers. Using idealized cluster merger simulations and mock shear catalogs matched to HSC and HST data, we find that weak-lensing mass estimates can systematically vary with the merger phase, introducing bias when we select cluster mergers at specific dynamical stages. Specifically, we find that the bias increases with the mass of the cluster, potentially leading to significant mass overestimation of massive clusters and affecting the high-mass end of the halo mass function. We will further extend this analysis by identifying cluster mergers in cosmological simulations and examine how the bias evolves under realistic structure formation with diverse merger configurations. Our results highlight the importance of mass calibrations in upcoming weak-lensing surveys for precision cosmology.