Ionisation, shocks, and evolution of the emission line gas of z ∼ 1 radio galaxies

From deep spectroscopic observations of a sample of powerful radio galaxies with redshifts z similar to 1, it is found that both the ionisation state and the kinematics of the emission line gas evolve strongly with the size of the radio source. Radio sources with small Linear sizes (less than or similar to 150 kpc) have emission line ratios in agreement with theoretical shock ionisation models whilst those of larger sources match photoionisation predictions. The emission line gas of small sources is also more luminous and has broader Line widths and more distorted velocity profiles than that of larger radio sources. The emission line properties of small radio sources appear to be dominated by the shocks associated with the radio source.