1994A&A...292...20R

Bidimensional spectroscopy of the distant (z=0.471) radio-galaxy 3C 435A has been performed with the integral field spectrograph TIGER at the CFHT. At least five components are identified around the central one. The [OII]3727A and [OIII]4959,5007A maps are remarkably superimposed with the 1.4 GHz radio lobe isophotes, showing the narrow relationship between the radio plasma and the ionised component, while the 4.8GHz radio emission traces a shock region. The [OII]/[OIII] ratio map follows the external part of the radio lobe rather than the central jet, and is strongly distorted by multiple components. This high number density is confirmed by the velocity field. The maximum ratio value (≃8) indicates a low level of ionisation. For the first time, stellar and nebular components are separated at a large redshift, indicating that the alignment effect is mainly due to nebular [OII] and [OIII] emission. With the help of our spectrophotometric model, the stellar continuum of the central component A is well fitted with an old (more than 15Gyrs at z=0) elliptical galaxy model, while nebular lines witness a faint star formation process. Two companions B and D, located near the radioaxis, fit evolved (≥10Gyrs) models, ruling out a current star formation activity induced by the radio-jet. Another companion, C, located in a direction roughly perpendicular to the radioaxis, has a blue color of irregular type, a few Gyr age, detectable emission lines and high velocity. Component E, roughly aligned with A and C, is essentially emitting in the [OII] line. Masses and magnitudes of some components are given and, among various radiogalaxy models, a scenario of ionised gas cocoon due to overpressure, or to interactions of the relativistic electrons with the intergalactic medium, with a possible axis-perpendicular gaseous disk, is favored.