Excitation of the Extended Gas in NGC 1068

Abstract

We present photoionization models of high exitation gas in the Extended Narrow Line Region (ENLR) of NGC 1068. The ENLR line fluxes have been calculated allowing for attenuation of the nuclear ionizing continuum as a function of distance from the central source. The diffuse continuum emission from the low density gas is also included as an important secondary source of ionizing radiation. The observed emission from high excitation gas, in the ENLR of NGC 1068, is reproduced by assuming the central luminosity to be 3.5 × 1044 erg s-1 between 1014.6 and 1018.4 Hz. The column density attenuating the central continuum is Nh=1022 cm-2. The predicted reflected continuum from the gas located at a distance of 1.5 kpc is about 10 % of the observed extended soft X-ray continuum in NGC 1068.