Left: Stellar-mass distribution for all galaxies in TNG100. The dashed line shows the limit log at which we consider galaxies to be “massive”. The orange bars comprise the core of our study sample. Right: Satellite (yellow)–central (purple) separation for galaxies with log₁₀M_⋆/M_⊙>10¹¹. Massive galaxies are predominantly central, though a non-negligible fraction are satellites.