Scatter plot of I([CII])_g versus I([NII])_s integrated intensities for radial velocity components listed in Table 2. Data points are shown as filled black circles, while model points satisfying 0.3 < [C/N]_AF/[C/N]_ON < 0.5 are shown in gray, with symbol shape and size depending on the gas physical parameters, as listed in the upper left corner of the figure. A least-squares fit to the model predictions yields log I([CII]_HII) = 1.068 × log I([NII]) + 0.645, shown by the gray straight line. For comparison, the expected [CII] emission contribution from H II regions in the Abel (2006) models for 1.0 Z_⊙ and 0.1 Z_⊙ are shown as dashed and dotted black straight lines, respectively.