Distribution of the S₁₀₀/S₂₄ colour among sources in the GOODS-H sample with spectroscopic redshift at 1.0 < z < 1.7. Green line and green shadowed area indicates the Gaussian fit to the distribution and the area beneath it. Coloured bars indicate the range of the S₁₀₀/S₂₄ colour of several observed SEDs of local LIRGs and ULIRGs at this redshift bin. The silicate optical depths of the local sources, as derived by IRS spectroscopy are also overlaid. The black arrow indicates the position of the high-z 24   μm dropout sample.