Oral Presentation

Tidal Evolution of Dark Matter Subhalos in z ∼ 1 Galaxy Clusters: Evidence from Galaxy–Galaxy Lensing

Author(s): Hye Gyeong Khim (Yonsei University), M. James Jee (Yonsei University, UC Davis), Kim HyeongHan (Yonsei University), and Jinhyub Kim (University of Oxford)

Presenter: Hye Gyeong Khim (Yonsei University)

Galaxy clusters at z ∼ 1 represent a key epoch in the growth of cosmic structure, marked by active accretion and pronounced tidal effects. This study presents the first direct measurement of subhalo masses in high-z galaxy clusters beyond unity. Through galaxy–galaxy lensing (GGL) of 28 clusters (0.8 < z < 1.5) with HST/ACS, we investigate how subhalos evolve under tidal forces.
Conventional GGL models overlook subhalo clustering, leading to biased mass estimates in dense regions. We refine the model to account for this effect by incorporating subhalo spatial correlations, correcting for contamination from neighboring structures, and improving the accuracy of subhalo mass estimates.
By analyzing shear signals, we identify a pronounced V-shaped trend in subhalo mass with a dip at intermediate luminosity and projected cluster-centric radii, which is absent in low-redshift studies. This feature likely signals ongoing tidal stripping during cluster infall.
Our results support a picture of hierarchical growth and progressive subhalo disruption. Future surveys with Euclid and Roman will expand this framework, offering more profound insight into subhalo evolution across cosmic time.