We present detailed long‐slit spectroscopic observations of a sample of four powerful radio galaxies, with high redshifts (0.47

Integral‐field spectroscopic observations are presented for three powerful radio galaxies, namely 3C 277.3 (Coma A; z= 0.0857), 3C 171 (z= 0.2384) and 3C 265 (z= 0.811), which are known to be undergoing jet–cloud interactions. The morphology, kinematics and ionization of the gas in the emission‐line structure of these sources are mapped and analysed. One‐dimensional spectra are also extracted and integrated over the different emission‐line regions in each galaxy. In two of the galaxies (3C 277.3 and 3C 171) the radio sizes are of similar extent to the emission‐line structure. For these, enhanced emission‐line regions are found associated with the radio structures, in addition to complex kinematics and low ionization states close to the radio hotspots, indicating that jet‐induced shocks disturb and ionize the gas. Interestingly, the bright – presumably shock‐ionized – emission‐line region coincident with the radio jet knot in 3C 277.3 shows quiescent kinematics and high ionization state. Possible explanations for this puzzling result are proposed. The images of 3C 171 and 3C 265 indicate that the lateral expansion of the cocoon has a significant effect on the kinematics and ionization of the gas, showing for the first time that the effects of the radio source are felt far from the jet axis. In addition, the presence of a stellar‐photoionized H ii region is detected in the extended emission‐line nebula of the radio galaxy 3C 277.3.

We present deep, narrow‐band and continuum images of the powerful high‐redshift radio galaxy 3C 265 (z=0.811), taken with the TAURUS Tunable Filter on the William Herschel Telescope, together with detailed long‐slit spectroscopic observations along the axis defined by the UV/optical emission elongation. The deep images reveal the existence of cones in the ionization structure of 3C 265 within ∼7 arcsec (58 kpc) of the nucleus, where the emission‐line structure is not observed to be closely aligned with the radio axis. This indicates that anisotropic illumination from the central active nucleus dominates on a small scale. In contrast, at larger distances (≳10 arcsec; 80 kpc) from the nucleus, low‐ionization emission gas is closely aligned with the radio axis, suggesting that jet–cloud interactions may become the dominant mechanism in the line‐emitting gas on a larger scale. Moreover, the presence of a high‐velocity cloud at 2.5 arcsec from the nucleus, close to the radio axis, indicates that even close to the nucleus (∼20 kpc) jet‐induced shocks have an important kinematic effect. However, spectroscopic analysis of this region reveals that the ionization state of the high‐velocity gas is similar to or higher than that of the surroundings, which is opposite to what we would expect for a cloud that has been compressed and accelerated by jet‐induced shocks. Our images show that, while on a large scale the low‐ionization emission‐line structures are aligned with the radio axis, on a smaller scale, where AGN‐photoionization dominates, the highest surface‐brightness structure is aligned with the closest companion galaxy (misaligned with the radio axis). This suggest that much of the emission‐line structure reflects the intrinsic gas distribution, rather than the ionization pattern imprinted by the radio jets or by illumination from the central AGN. Overall, our results underline the need for a variety of mechanisms to explain the properties of the extended emission‐line gas in the haloes of radio galaxies.