I have noted that the stellar masses of the Brightest Cluster Galaxies (BCGs) in the TNG simulations are approximately one order of magnitude greater than those obtained from observations. I would appreciate any explanation for this discrepancy.
This is a complex comparison to make with observational data, with many systematic uncertainties. The result is also dependent on the resolution of the simulations. I suggest as a starting point Pillepich+2018 (Figs 9, 11, 14, A1)
Thank you so much for your comment.