Comparison of radial profiles. Upper panel: Comparison between the average radial distributions of molecular gas for bins 1 and 5, which correspond to the subsets of galaxies showing the lowest and the highest concentration indices of molecular gas in the sample respectively. Lower panel: Same as the upper panel but comparing the average radial distributions of molecular gas for bins 1 and 7, which represent the highest and the lowest ends of the L_X distribution in the sample, respectively.