Temperature fluctuations and infrared emission from interstellar grains

The spectrum of infrared emission from interstellar dust grains is becoming known as a result of the recent successful mission of the Infrared Astronomy Satellite (IRAS) and the continuing ground-based and balloon-borne observations. The present paper has the objective to compute in detail the infrared emission expected from a graphite-silicate grain model, including the effects of temperature fluctuations, and to compare 'predicted' emission spectra with available observations. Details regarding the considered model are discussed, taking into account the radiation field, the grain models, the physical properties of the grains, and the method of calculation. Attention is given to temperature distributions and predicted emission, the IR emission from diffuse H I clouds, and the IR emission from dark clouds.