INFRARED-SPECTRA OF OBSCURING DUST TORI AROUND ACTIVE GALACTIC NUCLEI .1. CALCULATIONAL METHOD AND BASIC TRENDS

Using a new two-dimensional radiative transfer algorithm, we have calculated the thermally reradiated infrared spectra of the compact dust tori which are thought to surround many active galactic nuclei. These tori radiate anisotropically. Face-on tori may be from one-half to a few orders of magnitude brighter than edge-on tori throughout the infrared. Their spectra at nearly all viewing angles are basically "bumps" which are about 50% wider than blackbodies and peak in the mid-infrared at a wavelength determined mainly by the flux of nuclear radiation on the inner edge of the torus. The infrared color temperatures are hotter for face-on tori than edge-on tori by approximately 100 K. The 10 mum silicate feature often associated with dust can appear in absorption, emission, or not at all. There is a rough tendency for absorption features to be more prominent for edge-on tori than for face-on tori. In a subsequent paper we will compare these predictions with actual observations.