The core fundamental plane of B2 radio galaxies

Context. The photometric, structural and kinematical properties of the centers of elliptical galaxies harbour important information on the formation history of galaxies. In the case of non-active elliptical galaxies, these properties are linked in a way that surface brightness, break radius and velocity dispersion of the core lie on a fundamental plane similar to that found for their global properties.Aims. We construct the core fundamental plane (CFP) for a sizeable sample of low redshift radio galaxies and compare it with that of non-radio ellipticals.Methods. We combine data obtained from high resolution HST images with medium resolution optical spectroscopy to derive the photometric and kinematic properties of ~40 low redshift radio galaxies. Results. We found that the CFP of radio galaxies is indistinguishable from that defined by non-radio elliptical galaxies of similar luminosity. The characteristics of the CFP of radio galaxies are also consistent (same slope) with those of the fundamental plane (FP) derived from the global properties of radio (and non-radio) elliptical galaxies. The similarity of CFP and FP for radio and non-radio ellipticals suggests that the active phase of these galaxies has minimal effects on the structure of the galaxies.