Star formation rates in distant radio galaxies are crucial for
understanding the evolution of galaxies. Most processes at works in
these targets observed at the most remote epochs are directly or not
related to primeval sources of star formation: interplays of starbursts
and AGNs, interactions of radio jets with environmental clouds. cooling
flows, metal enrichment and dust distributions. Signatures of typical
star formation (emission line ratios, equivalent widths, stellar continua)
are observed in distant galaxies. However in most cases, they are superimposed
to signatures of other processes (shocks, AGN light scattering).
in particular at high z with the decrease of angular resolution
and surface brightness. A larger variety of environmental components
(lobes, jets, clouds and nucleus) simultaneously contribute to the global
emission. So that to separate the varions emission processes becomes
rapidly essential with higher distances. The 3D spectroscopy is unique
to disentangle the various physical processes triggering star formation
at high redshifts. Shocks and regions photoionized by the central AGN
are identified from their typical features and may be localized in the various
zones of the radio galaxy extended to its environment. We present
results of a long term observationnal prograin with the successive Integral
Field Units (IFU) TIGER and OASIS at CFHT. The present
sample consists of three galaxies of increasing z: 3C 171 {z = 0.238),
3C 435A (z = 0.470) and 4C 41.17 (z = 3.8). Line ratios, continua and
velocity fields are locallv measured. Interpretations of emission line ratios,
velocity fields, equivalent widths, are possible with a coupled code
based on CLOUDY and MAPPINGSIII results, as proposed by Moy
et al. (2000, 2001). Stellar and nebular continua are interpretcd with
the help of our evolutionary synthesis model PEGASE2. Ail models
take into account metallicity effects.