QSO hosts Searching for H-R diagram of QSO The redshift of BL Lacertae objects The core fundamental plane of radio galaxies

The core fundamental plane of radio galaxies

cfp_rg_fig
Figure 1: The CFP for the B2 radio galaxies (filled black circles) compared to a sample of nearby early type galaxies (open squares, Faber et al. 1997). The solid line represents the FP for a sample of RG (Bettoni et al. 2003)

One of the most important characteristic of early-type galaxies is that their global properties are fairly well described through a three dimensional space of observables, that involves the effective radius r_e, the corresponding average surface brightness and the central velocity dispersion sigma_c, the Fundamental Plane(FP). In addition the nuclear properties of nearby early type galaxies point out that the inner luminosity profiles of E galaxies are parametrized by break radius r_b and break surface brightness mu_b and they shows that there is a Core Fundamental Plane (CFP) analogous to the one found for the global properties of early type galaxies.

It is well known that massive early type galaxies may be associated with powerful radio emission and that their radio properties (power, morphology, etc) are related to the characteristic of the galaxies (luminosity, structure, environment, etc). In spite of these relationships the true role played by these different properties is not well known. In a previous work we have investigated the FP of low redshift radio galaxies and found it is consistent with the one defined by normal galaxies. (see)

In order to contribute to the understanding of the link between the powerful radio emission and the properties of their host galaxies we are undertaking a study of the Core Fundamental Plane (CFP) of low redshift radio galaxies and plan to compare it with that of similar elliptical galaxies that are not radio loud.

To this aim we combined photometrical and structural properties of a sample of 41 radiogalaxies obtained from high resolution HST images (de Ruiter et al. 2005) with kinematics measurements derived from new optical spectra. We find that the CFP of low-z radio galaxies is indistinguishable from the one of non radio elliptical galaxies (see figure). The properties of CFP of RG are also "consistent" with those derived from the photometric and structural properties of the whole galaxy the "global" Fundamental Plane (FP), of normal and radio galaxies. These results suggest that the cores of RG are in dynamical equilibrium supported by random motions, and that mass-to-light ratio in the core varies smoothly.

People: D. Bettoni, R. Falomo

Collaboration: H. de Ruiter(INAF-OA Bologna), P. Parma (INAF- IRA Bologna), R. Fanti (Univ. Bologna)

Recent Publications: Bettoni et al. (2007), ASPC 374,491