Abstract
We present HST/STIS long slit spectra of the aligned emission line nebulae in 3 powerful Compact Steep Spectrum (CSS) radio sources. We find systematic offsets in the line centroid on the two sides of the radio source of order 300 - -500 km s-1 with similar values for the line widths. We do not find evidence for Keplerian rotation curves. The spatial association of the velocity offsets with the radio lobes implies that the line offsets from systemic are most likely due to outflow driven by the radio source, suggesting that CSS radio sources are capable of accelerating ambient clouds up to velocities of 300 - -500 km s-1. We also present the first HST/STIS images of Ly alpha emission in a ``cooling flow'' radio source-PKS 2322-123. The moderate power radio source appears to be sweeping up gas in the north and to be deflected by a dense cloud in the south. The Ly alpha is brightest on the scale of the radio source which suggests that the radio source plays a role in determining the brightness of the inner Ly alpha emission-either by enhancing the emission measure through compression and/or by providing some of the energy to power the luminosity. The Ly alpha extends out to scales of 25 arcsec diameter with a diffuse, filamentary morphology and with a ``standard'' Ly alpha /H alpha ratio (except in some of the inner filaments)-implying that the dust has a low volume filling factor and is confined mainly to a few clumpy inner filaments. Thus, the more powerful CSS sources and the lower power ``cooling flow'' source have had qualitatively different interactions with their environment-although in both cases the emission line gas allows us to probe that interaction.
