Logarithmic ratio between the observed and modeled radio emission. The color scale is symmetric and increases in increments of 0.1 dex, red colors indicate a local radio excess, blue colors a radio deficit and gray areas are masked background sources. Magenta and green lines are the 5σ contours of B_obs and Σ_SFR, respectively. The black arrow indicates the approximate orbit of the galaxy as inferred from the direction of the tail. The circles in the bottom left correspond to the angular resolution of the radio data, which is 9″, except for IC 3105, IC 3258, NGC 4424, IC 800 and NGC 4654 where we used maps at 20″ resolution.