Infrared View of the Interstellar Medium

Variations in the diffuse infrared emission from the Galactic plane are investigated in the framework of the present dust model. It is shown that observations are interpreted in terms of superposition of emission from dust grains in various radiation field intensities. The superposition model can also be applied successfully to observations of the Large Magellanic Cloud as well as of external galaxies. Infrared spectroscopy of gaseous species provides information on the elemental compositions of interstellar dust grains. Recent observations indicate that part of silicon atoms reside in rather volatile components other than silicates, which may call for reconsideration of major components of interstellar dust grains. Latest observations with Spitzer and AKARI in a wide spectral range will further improve our understanding of the interstellar medium