Comparison of the BTFR to semi-analytic models in ΛCDM. Left panel: datapoints with errorbars are the galaxies in the α.btfr sample, color-coded by the kurtosis of their HI profile (same as in Fig. 6). The black solid line is the prediction for the BTFR based on the semi-analytic model of Trujillo-Gomez et al. (2011). The black dashed line represents the variant of the TG11 model that does not include adiabatic contraction of the dark halo due to the infall of baryons. Right panel: the magenta shaded region corresponds to the prediction for the shape and intrinsic scatter of the BTFR, according to the semi-analytic model of Desmond (2012, D12). Keep in mind that in both panels the rotational velocity of the model is defined in a different way than that for the α.btfr galaxies (refer to Sect. 5.2).