The core fundamental plane of radio galaxies
|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.
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)
Bettoni et al. (2007), ASPC 374,491