Emission-line properties of 3CR radio galaxies: Origins and implications of the velocity fields

We report on the results of a study of the kinematics and morphology of the emission line nebula in powerful 3CR radio galaxics. We find that both the inferred mass in emission line gas and the: mass required tu gravitationally induce the observed kinematics (the dynamical mass) appear to increase with redshift (or radio power). The maximum measured emission line velocity increases with projected distance from the radio galaxy nucleus. The sources with the highest maximum velocities are those with two independent kinematic systems present. These results are consistent with a picture in which (1) the mass of cold gas in the radio galaxy increases with increasing redshifts, (2) the size of the ionized region extends further out at higher redshift due to the selection of more powerful sources with more luminous central AGN, (3) the most powerful sources at high redshift are found in very deep gravitational potentials and/or the environments of powerful radio galaxies at high redshift are in a relatively young evolutionary state dominated by infall. Completely alternative models in which the kinematics are dominated by interactions with the radio source cannot be ruled out at this time, but are at least some part in determining the kinematics we observe.