Comparison of predicted L_acc (y-axis) given three calibrations established for the Hu α line and our measured line luminosities: L_{H I 7−6} (x-axis). The three curves reproduce these calibrations; the lower left box highlights the typical dynamical range over which they were derived, and the upper right box shows the contrasting line luminosity regimes of our sample, to which each calibration curve is extrapolated. The shaded areas correspond to the uncertainties of the Tofflemire et al. (2025) and Shridharan et al. (2026) calibrations. The coloured vertical lines show our measured L_{H I 7−6} values (Table 5), where two per region are displayed given the two M09 (dotted) and KP5 (dashed) extinction curves. L_bol values are indicated with triangles for each region, and corresponding L_{H I 7−6} are displayed up to eight times each region’s L_bol to give a sense of the maximum L_acc we can expect to still be physical (see Sect. 5.2). Error bars were omitted since the overall uncertainty is dominated by the two extinction curves.