Distribution of TNG50 and observed cluster galaxies in the phase-space of projected LOS velocity versus projected cluster-centric radius, color coded by the stellar age of the dynamically cold component. In particular, we compare Fornax cluster members (right) to cluster galaxies of the TNG50 halo with Group ID 2 (left), in a random projection. The boundaries of regions A, B, C, D, and E are defined as in Rhee et al. (2017). Both simulated and observed cluster galaxies exhibit similar trends, with galaxies closer to the cluster center typically having older stars in their disk components. The annotated numbers give the 25th–75th percentile ranges of the true infall time of the simulated galaxies in region E, D, and B+C, respectively.