Ratios of the exponential scale-lengths as a function of Hubble stage T: a: 70 μm/3.6 μm, b: 250 μm/3.6 μm, c: Σ_SFR/3.6 μm. In each panel, the (blue) large circles with error bars are the means over small ranges of Hubble stages (2–3, 4–5, 6–8) as indicated by the horizontal error bars, while the vertical error bars are the standard deviations. The horizontal dashed lines show the mean scale-lengths by averaging all galaxies.