A hot gas halo is predicted by chemodynamical models during the early evolution of spheroidal galaxies .
Cold condensations , arising from thermal instabilities in the hot gas , are expected to be embedded in the hot halo .
In the early phases of the galaxy ( t \la 1 Gyr ) , a strong X-ray and EUV emission is produced by the extended hot gas distribution , ionizing the cold clouds .
This self-irradiating two-phase halo model successfully explains several line ratios observed in QSO absorption-line systems , and reproduces the temperature distribution of Lyman- \alpha clouds .