Distribution of the parameters used to construct the control sample. Panels a–d: show the distribution of stellar surface density (logμ_*), stellar mass (log M_*), concentration (C), redshift (z), and effective radius (log R₅₀), respectively. Results for galaxies with strong spiral arms (2 + log s_arm ≥ 1.44) are marked in blue histogram, and the same for the control sample with weak spiral arms (2 + log s_arm <  1.44) are marked in gray filled histogram. The p value of the Kolmogorov–Smirnov test is presented at the top of each panel.