BTFR of gas-dominated, edge-on galaxies. Blue circles represent the 97 galaxies in the α.btfr sample, which is selected from the ALFALFA survey (see Sect. 2.1). The values of rotational velocity and baryonic mass, as well as their errors, have been computed as described in Sect. 3. The three outliers to the relation are marked by a red dot superimposed on their symbol. The thick dotted line represents the best linear fit to the BTFR (excluding outliers), which has a slope of α = 3.58 ± 0.11.