THE ORIGIN OF THE FAR-INFRARED CONTINUUM IN ACTIVE GALACTIC NUCLEI

A statistical approach is adopted to determine the origin of the far-infrared continuum in active galactic nuclei (AGNs). Infrared (IRAS) and optical properties of Markarian Seyferts are submitted to a comparative analysis together with those of starburst galaxies, here assumed to exemplify purely thermal emission. Distributions and various correlations are analyzed using survival analysis techniques to exploit the information in the censored data. This study shows no significant differences in infrared continuum properties between Seyfert 1s and Seyfert 2s. For a given galactic mass, both Seyfert types show an excess in mid- and far-infrared emission relative to starbursts. In agreement with previous work, statistical trends indicate that the infrared continuum in Seyfert galaxies is a composite of thermal and nonthermal emission. Finally, while at longer wavelengths Seyfert infrared continuum properties tend to be dictated by thermal emission, at 25-mu-m a nonthermal signature is evident.