Scale-by-scale correlation between the FIR emission and the observed 20 cm RC (top), the free-free (middle), and the synchrotron (bottom) emissions in NGC 6946. The horizontal line shows r_w = 0.5, the threshold for detecting a correlation. Larger r_w(a) corresponds to more highly correlated structures. These figures illustrate that, on scales smaller than 4 kpc, the FIR-synchrotron correlation is weaker than the FIR-free-free correlation.