Hubble Space TelescopeObservations and Photoionization Modeling of the LINER Galaxy NGC 1052

We present a study of available Hubble Space Telescope (HST) spectroscopicand imaging observations of the low ionization nuclear emission line region(LINER) galaxy NGC 1052. The WFPC2 imagery clearly differentiates extendednebular Halpha emission from that of the compact core. Faint ObjectSpectrograph (FOS) observations provide a full set of optical and UV data(1200-6800 Angstroms). These spectral data sample the innermost region (0."86 x 0."86 ~ 82pc x 82pc)and exclude the extended Halpha emission seen in the WFPC2 image. The derivedemission line fluxes allow a detailed analysis of the physical conditionswithin the nucleus. The measured flux ratio for Halpha/Hbeta,F{Halpha}/F{Hbeta}=4.53, indicates substantial intrinsic reddening,E(B-V)=0.42, for the nuclear nebular emission. This is the first finding of alarge extinction of the nuclear emission line fluxes in NGC 1052. If thecentral ionizing continuum is assumed to be attenuated by a comparable amount,then the emission line fluxes can be reproduced well by a simplephotoionization model using a central power law continuum source with aspectral index of alpha = -1.2 as deduced from the observed flux distribution.A multi-density, dusty gas gives the best fit to the observed emission linespectrum. Our calculations show that the small contribution from a highlyionized gas observed in NGC 1052 can also be reproduced solely byphotoionization modeling. The high gas covering factor determined from ourmodel is consistent with the assumption that our line of sight to the centralengine is obscured.Comment: 23 pages, 7 Postscript figures, 1 jpeg figure ; uses aaspp4.sty, 11pt to appear in The Astrophysical Journa