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We have examined the physical conditions within a bright emission-line knotin the inner narrow-line region (NLR) of the Seyfert 2 galaxy Mrk 573 usingoptical spectra and photoionization models. The spectra were obtained with theHubble Space Telescope/Space Telescope Imaging Spectrograph with the G430L andG750M gratings. Comparing the spatial emission-line profiles, we found [Fe X]6734 barely resolved, [O III] 5007 centrally peaked, but broader than [Fe X],and [O II] 3727 the most extended. The spectra reveal that [Fe X] is broader invelocity width and blue-shifted compared with lines from less ionized species.Our estimate of the bolometric luminosity indicates that the active galacticnucleus (AGN) is radiating at or above its Eddington Luminosity, which isconsistent with its identification as a hidden Narrow-Line Seyfert 1. We wereable to successfully match the observed emission line ratios with athree-component photoionization model. Two components, one to account for the[O III] emission and another in which the [Fe X] arises, are directly ionizedby the AGN, while [O II] forms in a third component, which is ionized by aheavily absorbed continuum. Based on our assumed ionizing continuum and themodel parameters, we determined that the two directly-ionized components are ~55 pc from the AGN. We have found similar radial distances for the centralknots in the Seyfert 2 galaxies Mrk 3 and NGC 1068, but much smaller radialdistances for the inner NLR in the Seyfert 1 galaxies NGC 4151 and NGC 5548.Although in general agreement with the unified model, these results suggestthat the obscuring material in Seyfert galaxies extends out to at least tens ofparsecs from the AGN.

Physical Conditions in the Inner Narrow Line Region of the Seyfert 2 Galaxy Markarian 573