THE 10 MICRON EMISSION OF SEYFERT NUCLEI

We examine the 10 mu m emission of the central regions of 117 Seyfert galaxies, after having compiled all the ground-based, small aperture (similar to 5'') photometric observations at lambda similar to 10 mu m (N-magnitudes) published in the literature. We also evaluate the compactness of the 10 mu m emission through a comparison of these small-beam measures with the large beam IRAS 12 mu m fluxes. We apply survival analysis statistical techniques in order to exploit the information contained in ''censored'' data (i.e., upper limits on fluxes). Seyfert galaxies appear to have more compact and powerful central 10 mu m emission than non-Seyfert galaries have. Interactions do not affect appreciably the 10 mu m emission of Seyfert galaxies. Their 10 mu m emission, which is quite weakly related to the X-ray emission, correlates well with the nuclear non-stellar near-infrared emission and with the IRAS 12 and 25 mu m band emissions, less well with the IRAS 60 mu m emission and even worse with the IRAS 100 mu m emission. The 100 mu m to 25 mu m global energy distribution flattens systematically with increasing 10 mu m luminosity. Seyferts 1 have, on average, greater 10 mu m luminosity than S2 have, but similar surface brightness and compactness. Seyferts 2 have steeper continuum spectra between 12 and 25 mu m than Seyferts 1 have. Our results favour thermal dust emission models for the origin of the mid-infrared emission of Seyfert galaxies. Within the context of unified schemes of Seyfert galaxies, our findings support the presence of a moderate amount of anisotropy in the 10 mu m emission and are consistent with the presence of Thomson optically thin obscuring dust tori around Seyfert nuclei.