The spectra of the powerful 3CR radio galaxies present a typical distribution in the far-infrared ( FIR ) .
From the observed radio to X-ray spectral energy distribution ( SED ) templates , we propose to subtract the typical energy distributions of , respectively , the elliptical galaxy host and the synchrotron radiation .
The resulting SED reveals that the main dust emission is well fitted by the sum of two blackbody components at the respective temperatures 340K \pm 50K and 40K \pm 16K .
When the AGN is active , the energy rate released by hot dust is much more dissipative than cold dust and stellar emission , even when the elliptical galaxy emission is maximum at age of \simeq 90 Myr .
Hot dust appears as a huge cooling source which implies an extremely short time-scale t _ { cool } .
In balance , with the short gravitational time-scale t _ { grav } of massive galaxies , the dissipative self-gravitational models ( Rees & Ostriker , 1977 ) are favoured for radio sources .
They justify the existence of massive radio galaxies at z =4 ( Rocca-Volmerange et al. , 2004 ) .
The synchrotron emission is emitting up to the X-ray wavelength range , so that strong ” EXOs ” sources could be assimilated to 3CR radio sources .
This analysis applied to ISO and SPITZER data on a larger sample will statistically confirm these results .