Lyman alpha systems within hot galactic haloes

A hot-gas halo is predicted by chemodynamical models during the early evolu tion of spheroidal galaxies. Cold condensations, arising from thermal insta bilities in the hot gas, are expected to be embedded in the hot halo. In th e early phases of the galaxy (t less than or equal to 1 Gyr), a strong X-ra y and EW emission is produced by the extended hot-gas distribution, ionizin g the cold clouds. This self-irradiating two-phase halo model successfully explains several line ratios observed in QSO absorption-line systems, and r eproduces the temperature distribution of Lyman alpha clouds.