Surface brightness profiles for our Hα (green) and Paα (turquoise) stacks (top row) with their ratios (bottom row) and Kendall’s Tau (τ) correlation statistics. The horizontal dotted line shows the expected Paα/Hα line ratio for Case B recombination (T_e = 10 000 K and n_e = 100 cm⁻³ based on photoionisation modelling with CLOUDY (Ferland et al. 2017)). Declining Paα/Hα with galactocentric radius in our highest- and lowest-mass bins highlights the additional dust-obscured star formation that Paα traces closer to galactic centres, which decreases towards the outskirts.