Relations between stellar and halo mass in our galaxy sample. The left panels show M_* vs. M₂₀₀, while the middle and right panels show ${\stackrel{\sim }{f}}_{*}$ as a function of M₂₀₀ and M_*, respectively. The observations are colour-coded by the log(M_gas/M_*) ratio. All panels highlight the cosmological baryon fraction f_{bar, cosmic}. In the bottom panels, we contrast our observations against the abundance-matching model of Moster et al. (2010), the semi-empirical DarkLight model (light green, Kim et al. 2024a) and the TNG50 (cyan, Nelson et al. 2019) and Simba (orange, Davé et al. 2019) cosmological hydrodynamical simulations. The bottom panels highlight a population of observed baryon-deficient dwarfs (BDDs, squares enclosing circles), characterised by having stellar masses more than one order of magnitude below abundance-matching expectations (plum region).