The emission line properties of the 3CR radio galaxies at redshift one:: Shocks, evolution, and the alignment effect

The results of a deep spectroscopic campaign on powerful radio galaxies with redshifts z similar to 1, to investigate in detail their emission line gas properties, are presented. Both the 2-dimensional velocity structure of the [OII] 3727 emission line and the ionisation state of the gas are found to be strongly dependent upon the linear size (age) of the radio source in a manner indicative of the emission line properties of small (young) radio sources being dominated by the passage of the radio source shocks. The consequences of this evolution throughout the few X 107 year lifetime of the radio source are discussed, particularly with relation to the alignment of the UV-optical continuum emission of these objects along their radio axis, the nature of which shows similar evolution.