Morphology of Galaxy Clusters and Sunyaev-Zel'dovich effect
  Observations of the X-ray band wavelength reveal an evident ellipticity of many galaxy clusters atmospheres. The modeling of the intracluster gas with an ellipsoidal $\beta$-model leads to different estimates for the total gravitational mass and the gas mass fraction of the cluster than those one finds for a spherical beta-model. An analysis of a recent Chandra image of the galaxy cluster RBS797 indicates a strong ellipticity and thus a pronounced aspherical geometry. A preliminary investigation which takes into account an ellipsoidal shape for this cluster gives different mass estimates than by assuming spherical symmetry. We have also investigated the influence of aspherical geometries of galaxy clusters, and of polytropic profiles of the temperature on the estimate of the Hubble constant through the Sunyaev-Zel'dovich effect. We find that the non-inclusion of such effects can induce errors up to 40 per cent on the Hubble constant value. 
Ph. Jetzer (Univ. of Zurich-CH), P. Koch (Univ. of Zurich-CH), R.   Piffaretti (Univ. of Zurich and PSI-CH), D. Puy (Univ. o...