Optical and UV Spectral Diagnostics for GPS and CSS Sources

Abstract

In this paper I examine the use of optical and UV spectral diagnostic ratios to distinguish between gas which is locally shock-excited by the interaction with a jet and that which is photoionised by the central engine. In many cases key UV lines remain unobserved except in the case of high redshift radio galaxies. However, in one case, the nearby GPS galaxy NGC1052, UV data was obtained with the FOS. This object shows LINER characteristics at optical wavelengths, but has a rich coronal-line spectrum in the UV. We conclude that jet-driven shocks tend to evolve from shock-excited to photoionised later in their evolution.