Hubble Space Telescope observations and photoionization modeling of the liner galaxy NGC 1052

We present a study of available Hubble Space Telescope (HST) spectroscopic and imaging observations of the low-ionization nuclear emission-line region (LINER) galaxy NGC 1052. The WFPC2 imagery clearly differentiates extended nebular Her emission from that of the compact core. Faint Object Spectrogr aph (FOS) observations provide a full set of optical and UV data (1200-6800 Angstrom). These spectral data sample the innermost region (0."86 x 0."86 similar to 82 x 82 pc) and exclude the extended H alpha emission seen in th e WFPC% image. The derived emission-line fiuxes allow a detailed analysis o f the physical conditions within the nucleus. The measured flux ratio for H alpha/H beta, F-H alpha/F-H beta = 4.53, indicates substantial intrinsic r eddening, E(B-V) = 0.42, for the nuclear nebular emission. This is the firs t finding of a large extinction of the nuclear emission-line fluxes in NGC 1052. If the central ionizing continuum is assumed to be attenuated by a co mparable amount, then the emission-line fluxes can be reproduced well by a simple photoionization model using a central power-law continuum source wit h a spectral index of alpha = -1.2 as deduced from the observed flux distri bution. A multidensity, dusty gas gives the best fit to the observed emissi on-line spectrum. Our calculations show that the small contribution from a highly ionized gas observed in NGC 1052 can also be reproduced solely by ph otoionization modeling. The high gas covering factor determined from our mo del is consistent with the assumption that our line of sight to the central engine is obscured.