Mid-Infrared Infrared Space Observatory Spectroscopy of the Prototypical LINER NGC 1052: Shocks Reconsidered

Abstract

We have observed the prototypical LINER NGC 1052 with the Infrared Space Observatory Short-Wavelength Spectrometer. While we have detected the [Ne II] 12.8 μm line, we have obtained a strict upper limit for the [Ne III] 15.6 μm line. A large [Ne II]/[Ne III] line ratio and small [Ne III]/[O III] λ5007 and [Ne II]/[OIII] line ratios are consistent with slow-shock models with ~130 km s^-1 shock velocity. Our results support the original suggestions of shock excitation as a dominant source for NGC 1052. We have fitted the infrared and optical line ratios with a combination of shock and photoionization models. The best combination among the simple models we considered suggests that the contribution of shock and photoionization to [O III] λ5007 emission is four-fifths and one-fifth, respectively.