Hot Dust and the Near-Infrared Bump in the Continuum Spectra of Quasars and Active Galactic Nuclei

It is shown here that thermal radiation by dust can reproduce the overall shape of the bump seen in the near-infrared continua of many QSOs and AGN. A simple model in which dust grains are heated by the primary nuclear optical/ultraviolet continuum produces the required emission at short wavelengths. The model naturally explains the onset of the bump at about 2 microns. This wavelength corresponds to the optically thin emission peak for the hottest possible grains, i.e., graphite grains at their evaporation temperature near 1500 K. Emission longward of 2 microns is due to cooler grains farther from the central source. 33 references.