My task in reviewing interstellar dust in galaxies is greatly simplified by the appearance of several excellent review articles on this area during the past year or so. Although each covers only a specific aspect of the subject, together they comprise a good introduction to our current knowledge.
A comprehensive review of infrared emission from our Galaxy, with much historical background, has been given by Cox and Mezger (1989). They emphasize that the results from IRAS have led to a major reappraisal of estimates of the fraction of the infrared emission from our Galaxy which comes from interstellar dust illuminated by the interstellar radiation field, as opposed to regions of massive star formation. The latter are now believed to contribute only about 10% of the total infrared emission from the Galaxy. Boulanger and Perault (1988) have given an authoritative discussion of the infrared emission observed by IRAS from the different components of diffuse emission from our Galaxy, and the correlations between them, which must be the starting point for any analysis of the interstellar dust in normal galaxies. A general review of the IRAS view of the extragalactic sky has been given by Soifer et al (1987). Telesco (1988) has reviewed enhanced star formation and infrared emission in the centers of galaxies, with a strong emphasis on imaging and spectroscopic data derived from ground-based studies. Helou (1989) has reviewed the far infrared emission from Galactic and extragalactic dust seen by IRAS, emphasizing the similarity in the range of far infrared colors seen in external galaxies and in reflection nebulae in our Galaxy. Roche (1988) has given an interesting summary of the results from near and middle infrared spectroscopy of galaxies. Puget and Leger (1989) have given a very thorough review of the evidence for small grains and large aromatic molecules in the interstellar medium of our own and other galaxies. Finally Draine (1989) has reviewed interstellar extinction in the infrared.
In this review I shall concentrate on those areas where major controversy exists and where significant progress may be expected in the next few years. The topics I have selected are grain models, first attempts to explain the infrared spectra of IRAS galaxies, the destruction of the very small grain component, a new picture of interstellar dust in galaxies, results from far infrared and submillimeter mapping of galaxies, determination of the dust mass in galaxies, and dust in ellipticals and lenticulars.