a–d, The baryonic Tully–Fisher relation between the observed mass in stars and gas, Mb, and the flat rotation velocity Vf from our analysis1 (a) and that of ref. 3 (b). Blue points show high-quality data with distance uncertainties less than 20% and excluding the worst rotation curves (Q = 3 in SPARC2). Crosses show the remaining data. The data follow a line of constant a0 = 1.2 × 10–13 km s–2 (ref. 6). Each galaxy has g† = xVf4/(GMb) (ref. 8), where G is Newton’s constant and x = 0.8 accounts for the disk geometry of rotating galaxies9. The line is not a fit; it simply shows g† = a0. Scatter around this line is shown in c and d. Grey histograms include all available data; blue histograms are restricted to higher-quality data as defined above. The red histogram in d shows the fitted a0 of ref. 3.