The multitude of unresolved continuum sources at 1.6 microns in Hubble Space Telescope images of Seyfert galaxies

We examine 112 Seyfert galaxies observed by the Hubble Space Telescope at 1.6 mum. We find that similar to 50% of the Seyfert 2.0 galaxies which are part of the Revised Shapely-Ames (RSA) Catalog or the CfA redshift sample contain unresolved continuum sources at 1.6 mum. All but a couple of the Seyfert 1.0-1.9 galaxies display unresolved continuum sources. The unresolved sources have fluxes of order 1 mJy, near-infrared luminosities of order 10(41) ergs s(-1), and absolute magnitudes M-H similar to -16. Comparison non-Seyfert galaxies from the RSA Catalog display significantly fewer (similar to 20%), somewhat lower luminosity nuclear sources, which could be due to compact star clusters. We find that the luminosities of the unresolved Seyfert 1.0-1.9 sources at 1.6 mum are correlated with [O III] lambda 5007 and hard X-ray luminosities, implying that these sources are nonstellar. Assuming a spectral energy distribution similar to that of a Seyfert 2 galaxy, we estimate that a few percent of local spiral galaxies contain black holes emitting as Seyferts at a moderate fraction, similar to 10(-1)-10(-4), of their Eddington luminosities. We find no strong correlation between 1.6 km fluxes and hard X-ray or [O III] lambda 5007 fluxes for the pure Seyfert 2.0 galaxies. These galaxies also tend to have lower 1.6 km luminosities compared to the Seyfert 1.0-1.9 galaxies of similar [O III] luminosity. Either large extinctions are present toward their continuum- (A(V) similar to 20-40) emitting regions or some fraction of the unresolved sources at 1.6 km are compact star clusters. With increasing Seyfert type the fraction of unresolved sources detected at 1.6 km and the ratio of 1.6 km to [O III] fluxes tend to decrease. These trends are consistent with the unification model for Seyfert 1 and 2 galaxies.