Imaging spectrophotometry of ionized gas in NGC 1068. III - Anisotropic excitation of the large-scale disk by scattering of nuclear continuum

Abstract

Photoionization of the solar abundance diffuse ionized media (DIM) inNGC 1068 by anisotropic nuclear emission is studied. It is shown thatthe emission characteristics can be understood in the light of thedeveloping picture of the galaxy in which its intrinsic type 1 Seyfertnucleus, concealed by an obscuring medium, is visible only throughscattered, polarized light. The gas excitation is anisotropic, thehigh-excitation gas along the jet axis being photoionized by directnuclear continuum, while the lower excitation gas away from the axissees only indirect nuclear emission scattered into it. A model of lowoptical depth, near-nuclear Thomson scattering is considered in detail,and it is shown that, even with moderate dust extinction, this mechanismis sufficient to energize the DIM.