Spectroscopic follow-up of FIRBACK-South bright galaxies

Clusters of galaxies contain a fair sample of the universal baryonic mass fraction. A combined analysis of the intracluster medium (ICM) within their hydrostatic regions, as derived from both Sunyaev-Zeldovich effect (SZE) measurements and X-ray images, makes it possible to constrain the cosmological parameters. We consider both gas fraction estimates and angular diameter distance measurements. Adopting median statistics, we find, at the 2-(sigma) level, the pressureless matter density, (omega) MO, to be between 0.30 and 0.40 and the Hubble constant, H0, between 44 and 66 km s-1 Mpc-1.