IRAS Observations of Starburst and Nonactive Spiral Galaxies

Far-infrared properties of starburst, Seyfert II, and nonactive spiral galaxies are analyzed using IRAS observations at 25, 60, and 100 microns. Both starburst galaxies and nonactive spirals concentrate in a small area in IR color-color diagrams. These observed colors can be interpreted in terms of a cool (about 30 K) disk component plus a warm (about 80-90 K) component. The total IR luminosities of the starburst galaxies range from 10 to the 10th to 10 to the 12th solar luminosities, while the upper limit of nonactive spiral galaxies is about 10 the 11th solar luminosities. The IR color of the starburst galaxies is that of a normal spiral galaxy plus a larger warm component contribution. The 60 micron flux is 10-20 percent larger than in the nonactive spirals of this sample. The fraction of 60-micron emission attributable to the warm component can be used as an indicator for the star-formation activity in galaxies.