Interstellar Dust Models for Extinction and Emission

A new coherent interpretation of the interstellar extinction and the IR emission is proposed which uses an empirical dust model made of big grains, very small grains, and polycyclic aromatic hydrocarbons. It is argued that the big grain component is probably made of a size distribution of silicates with some dark refractory mantle and that very small gains are probably carbon-dominated. The variations of IR colors with the intensity of the incident radiation field is studied in various astrophysical situations. Correlations between anomalous extinction curves and anomalous IR colors are predicted.