The infrared (2–800 μm) spectral energy distribution of the spiral galaxy M100 (NGC 4321). The solid line is, among the Draine & Li (2007) dust models, the one better fitting the observed data (filled dots). The IRAS 60 and 100 μm bands sample the dust emitting at wavelengths shorter than the wavelength of the peak (~150 μm) and are thus sensitive to the emission of the warm dust. The SPIRE bands at 250, 350 and 500 μm cover the Rayleigh-Jeans tail of the dust emission (cold dust).