Radio-FIR relation for the low-frequency MSSS (left) and high-frequency NVSS data (middle). The red, blue and green symbols represent faint, medium bright, and bright NVSS galaxies, respectively. The MSSS–NVSS luminosity diagram is shown on the right. The solid line is a bisector fit, while the dashed lines represent simple X vs. Y and Y vs. X linear regressions in the logarithmic space of the parameters.