The fundamental plane of radio galaxies^*

¹ Osservatorio Astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy e-mail: falomo@pd.astro.it; fasano@pd.astro.it; salvo@pd.astro.it
² Istituto di Radioastronomia di Bologna and Dipartimento di Astronomia, Universitá di Bologna, Italy e-mail: fgovoni@ira.bo.cnr.it
³ European Southern Observatory e-mail: rscarpa@eso.org

Corresponding author: D. Bettoni, bettoni@pd.astro.it

Received: 10 September 2001
Accepted: 15 October 2001

Abstract

We collected photometrical and dynamical data for 73 low red-shift () Radio Galaxies (LzRG) in order to study their Fundamental Plane (FP). For 22 sources we also present new velocity dispersion data that complement the photometric data given in our previous study of LzRG (Govoni et al. [CITE]a). It is found that the FP of LzRG is similar to the one defined by non-active elliptical galaxies, with LzRG representing the brightest end of the population of early type galaxies. Since the FP mainly reflects the virial equilibrium condition, our result implies that the global properties of early-type galaxies (defining the FP) are not influenced by the presence of gas accretion in the central black hole. This is fully in agreement with the recent results in black hole demography, showing that virtually all luminous spheroidal galaxies host a massive black hole and therefore may potentially become active. We confirm and extend to giant ellipticals the systematic increase of the mass-to-light ratio with galaxy luminosity.