Some New Observed Properties of Elliptical Galaxies |
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Authors: | D Gerbal HV Capelato F Durret GB Lima Neto I Márquez |
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Institution: | 1. Institut d'Astrophysique de Paris, (CNRS), 98bis, Bd Arago, F-75014, Paris, France 2. DAEC, Observatoire de Paris, Universite Paris VII – CNRS, F-92195, Meudon cedex, France 3. Instituto de Pesquisas Espaciais, Sao Jose dos Campos/SP, S?o Paulo, Brazil 4. Instituto Astron?mico e Geofísico/USP, Av. Miguel Stefano 4200, Sao-Paulo/SP, Brazil 5. Instituto Astrofisica de Andalucia, (, CSIC, Apartado 3004, E-18080, Granada, Spain
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Abstract: | We suggest that elliptical galaxies, as stellar systems in a stage of quasi-equilibrium, may have a specific entropy. We use
the Sérsic law to describe the light profile. The specific entropy (the Boltzmann–Gibbs definition) is then calculated assuming
that the galaxy behaves as a spherical, isotropic, one-component system. We predict a relation between the three parameters
of the Sérsic law linked to the specific entropy, defining a surface in the parameter space, an ‘entropic plane’. We have
analysed a sample of simulated merging elliptical galaxies (virtual) and a sample of galaxies belonging to the Coma Cluster (real). Both virtual and realgalaxies are: 1) located 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 small
increase in the specific entropy with the generation after merging (virtual sample). Although one cannot distinguish between various generations for real galaxies, the distribution of specific entropy in this sample is very similar to that in the virtual sample.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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