Two physical laws for Elliptical galaxies: photometrical consequences
نویسنده
چکیده
In the present paper, we show that elliptical galaxies (Es) obey two laws. The first one accounts for the fact that Es are relaxed systems in a post violent-relaxation stage; they are quasi-equilibrium gravitational systems and therefore have a quasi-constant specific entropy. The second physical law is a scaling relation between potential energy and mass. Assuming that light traces mass, these laws imply that in the space defined by the three Sérsic law parameters (intensity Σ0, scale a and shape ν), elliptical galaxies are distributed on two 2-manifolds: the Entropic Surface and the Energy-Mass Surface. Using a sample of 132 galaxies belonging to three nearby clusters, we have verified that ellipticals do indeed follow these laws, and their dispersion about the two surfaces is very small. This also implies that they tightly distribute along the intersection line DAEC, Observatoire de Paris, Université Paris VII, CNRS (UA 173), F-92195 Meudon Cedex, France
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