The entropy of elliptical galaxies in Coma: a clue for a distance indicator

Abstract

We have fitted the surface brightness of a sample of 79 elliptical galaxies pertaining to the Coma cluster of galaxies using the Sersic profile. This model is defined through three primary parameters: scale length (a), intensity (Σ_0), and a shape parameter (ν); physical and astrophysical quantities may be computed from these parameters. We show that correlations are stronger among primary parameters than the classical astrophysical ones. In particular, the galaxies follow a high correlation in νand a parameters. We show that the νand a correlation satisfies a constant specific entropy condition. We propose to use this entropy relation as distance indicator for clusters.

5 pages, 3 figures, submitted to MNRAS Letters

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