Some new observed properties of elliptical galaxies

We suggest that elliptical galaxies, as stellar systems in a stage of quasi -equilibrium, may have a specific entropy. We use the Sersic law to describ e the light profile. The specific entropy (the Boltzmann-Gibbs definition) is then calculated assuming that the galaxy behaves as a spherical, isotrop ic, one-component system. We predict a relation between the three parameter s of the Sersic law linked to the specific entropy, defining a surface in t he parameter space, an `entropic plane'. We have analysed a sample of simul ated merging elliptical galaxies (virtual) and a sample of galaxies belongi ng to the Coma Cluster (real). Both virtual and real galaxies are: 1) locat ed in their own `entropic plane' and 2) in this plane, they are located on a straight line, indicating constant entropy: another physical property. A careful examination of the value of the specific entropy indicates a very s mall increase in the specific entropy with the generation after merging (vi rtual sample). Although one cannot distinguish between various generations for real galaxies, the distribution of specific entropy in this sample is v ery similar to that in the virtual sample.