Top row: the stellar density maps of one cluster-sized halo in the TNG50-1 simulation, projected onto the X−Y plane, zoomed in to show details at different radial scales from left to right. Shell-like density bumps are evident in these density maps, for example, around 500 ckpc h⁻¹, 300 ckpc h⁻¹, and 100 ckpc h⁻¹. The stellar particles associated with subhalos are grouped in white blobs in these figures. Middle row: phase-space diagram (radial velocity versus radial distance) of the diffuse stellar particles (excluding the subhalos shown in the top row), zoomed in to show details at different radial scales from left to right. The shell-like structures become more prominent in this diagram. Bottom row: 3D (first panel) and 2D projected density profiles (third panel) of the cluster stellar contents, and their radial slopes (second and fourth panels). Shell-like density bumps in the density and phase-space diagrams often correspond to dips and bumps in the density profiles.