IR8 = /L_8   μm ratio as a function of L_8   μm for star-forming galaxies, excluding recognized X-ray/optical AGN and infrared power-law AGN. The plain and dashed horizontal lines show the center and width of the Gaussian distribution of main sequence galaxies (Fig. 9 and Eq. (5)). Upper panel: position of the star-forming galaxies as measured. Most fall on the same sequence as local star-forming galaxies. Bottom panel: position of the same galaxies after correcting their IR8 ratio for starburstiness (unless 0.5  ≤  R_SB  ≤  2, where R_SB is consistent with unity within the error bars).