A simple analytical model for estimating the fraction (\Omega_{ gas}) of matter in gaseous form within the collapsed dark matter (DM) haloes is presented. The model is developed using (i) the Press-Schechter formalism to estimate the fraction of baryons in DM haloes, and (ii) the observational estimates of the star formation rate at different redshifts. The prediction for \Omega_{ gas} from the model is in broad agreement with the observed abundance of the damped Ly-\alpha systems. Furthermore, it can be used for estimating the circular velocities of the collapsed haloes at different redshifts, which could be compared with future observations.
Categories: astro-ph