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S.B. Kraemer (CUA/GSFC), L.C. Ho (Carnegie Observatories), D.M. Crenshaw (CUA/GSFC), A. V. Filippenko (Univ. of California, Berkeley), J.C. Shields (Univ. of Ohio)
We have combined ground-based optical and ISO spectra with Hubble Space Telescope/Faint Object Spectrograph data to study the emission line gas in the dwarf Seyfert 1 galaxy, NGC 4395. We have generated multicomponent photoionization models, the predictions of which support the suggestion that the emission-line gas is photoionized by a strong source of non-thermal EUV radiation arising from the core of the AGN. The narrow-line spectrum is well fitted by a simple three-component model, while an additional component was required to fit the broad lines. Models with elemental abundances approximately 1/2 solar, with even greater underabundance of nitrogen, provided the best fit to the data, and are in general agreement with estimates from studies of HII regions within NGC 4395. Much of the emission line gas in the NLR appears to be dusty, and there may be a significant amount of obscured gas, as evidenced by the strength of IR fine structure lines such as [O~IV] 25.9\mu and [S~IV] 10.5\mu. Assuming a central source luminosity determined by a fit to the observed UV and X-ray continuum fluxes, the models predict a covering factor of the emission line gas greater than unity, indicating that the observed continuum has been absorbed. The implications of the small size and mass associated with this mini-AGN are discussed.