The extended narrow-line region of the Seyfert 1 galaxy ESO 362-G18 versusthat of the Seyfert 2 galaxy ESO 362-G8

We use long-slit spectroscopic data to study in detail the extended narrow- line regions (ENLRs) of the Seyfert 1 galaxy ESO 362-G18 and Seyfert 2 gala xy ESO 362-G8. These two galaxies have similar emission-line luminosities a nd extents of the ENLR (similar to 4 kpc), whose shapes in previous narrowb and [O III] images suggest anisotropic escape of the nuclear ionizing radia tion as expected for shadowing by a nuclear torus in the framework of the u nified model. In the Seyfert 1 galaxy the high-excitation gas shows an appr oximately cone-shaped morphology. From the observed kinematics, we conclude that the gas within the cone most probably belongs to the galaxy disk, whi ch implies that the collimation axis is closer to the disk than half the op ening angle of the cone of ionizing radiation. In the Seyfert 2 galaxy, the main structure in the high-excitation gas is an emission blob which appare ntly consists of a high-latitude cloud being blown away from the nuclear re gion and ionized by the nuclear source. We use the radial distribution of stellar population features in order to e xtrapolate this population to the nucleus and isolate the optical continuum of the nuclear source. We obtain a featureless power-law continuum F-v pro portional to v(-0.76) for the Seyfert 1 galaxy, while for the Seyfert 2 gal axy we conclude that the nuclear bluer color and smaller equivalent widths of the absorption lines are due to an aging burst of star formation (age ap proximate to 300 Myr) and that the nuclear source is hidden from direct vie w. Using the photoionization code MAPPINGS Ic and a mixture of matter-bounded (MB) and ionization-bounded (IB) clouds, we model the ENLRs of the two gala xies. We use all the observables, mostly the emission-line fluxes as a func tion of distance from the nucleus and the optical nuclear continuum observe d in the Seyfert 1 galaxy as well as its X-ray flux, to constrain the param eters of a self-consistent model for the ENLR. For both galaxies, we conclu de that a power-law ionizing continuum F-v proportional to v(-1.2) better r eproduces the high-excitation lines near the nucleus than a multisegmented power law used in previous works. For the Seyfert 1 galaxy ESO 362-G18, the inferred luminosity of the ionizing continuum can be reconciled with the f lux observed in the optical, while in the X-rays the observed flux is simil ar to 100 times weaker than that necessary to reproduce the line fluxes, su ggesting that the X-ray continuum is absorbed toward Earth. For the Seyfert 2 galaxy ESO 362-G8, the inferred ionizing continuum when extrapolated to the optical implies a minimum obscuration toward the nuclear source of A(V) approximate to 4.0 mag. In the hypothesis of an isotropic nuclear source, in order to better constr ain the model parameters, we have adopted symmetrical physical conditions a s a function of distance on both sides of the nucleus: namely, the ionizing flux, the temperature, density, and ionization parameter of the MB gas, an d the metallicity. The radial density behavior of the IB gas was observatio nally inferred from the CS nl doublet ratio. The only free parameter, which was allowed to vary independently, was the relative proportion of the MB a nd IB emission-line components along the ENLR. The high-excitation gas with in the cone of ESO 362-G18 and within the blob of ESO 362-G8 have been mode led as regions of larger mass contribution from the MB component relative t o other locations of the ENLR. We derive the filling factors, covering factors, and gas masses along the E NLR as a function of distance from the nucleus. A comparison between the mo del results for the two galaxies shows that, around the nucleus, the Seyfer t 1 galaxy has a larger excitation due to a larger contribution of the MB c omponent. However, in the cone, the excitation is lower than in the blob of the Seyfert 2 galaxy due to a combination of a lower ionizing flux and lar ger gas density in the disk of the Seyfert 1 galaxy. The total ionized gas mass derived for the blob in the Seyfert 2 galaxy is 10(5.8) M-circle dot, consistent with its proposed origin in a nuclear superwind which probably o ccurred similar to 300 Myr ago, while the ionized gas mass in the disk of t he Seyfert 1 galaxy is 1 order of magnitude smaller.