Advanced Studies Diploma dissertation:

Université Denis Diderot (Paris VII) -
Institut d'Astrophysique de Paris (IAP)
June 2000, Paris, France

Author: Ricardo Demarco
Advisors: Dr. Florence Durret (IAP) & Dr. Daniel Gerbal (IAP)

The Specific Entropy of X-ray Galaxy Clusters

ABSTRACT:   It has been shown that self-gravitating systems such as elliptical galaxies have a constant specific entropy and obey a scaling law relating their potential energy to their mas, properties which might be due to the physical precesses involved in the formation of these structures. Since the X-ray gas in clusters is weakly dissipative, we have checked the hypothesis that it might verify similar properties. We have analyzed ROSAT-PSPC images of 15 clusters, fitting the density profile of the intra-cluster gas by a Sérsic law. We found that: 1) all these clusters roughly have the same specific entropy and 2) a scaling law linking the potential energy to the mass of the X-ray gas is observed, with the same slope as that found in elliptical galaxies. We also found that the Sérsic law parameters (intensity, shape and scale) are correlated two by two.