Comparison of the linear fit to the BTFR of the full α.btfr sample with and without intrinsic scatter included in the model. Comparison of the linear fit to the BTFR of the full α.btfr sample with and without intrinsic scatter included in the model. The layout of the figure follows that of Fig. 2. The thick dotted line represents our fiducial no-scatter fit, and is the same as the thick dotted line in Fig. 2. The thin solid line represents the best fit line when intrinsic scatter is treated as a free parameter. The gray shaded bands represent the 1σ and 2σ intrinsic scatter regions according to the best fit value of the parameter σ_{⊥ ,intr} = 0.045 dex.