2.30 pm Monday 12 November 2001
I will describe a model for the evolution of the thermodynamic properties of the intergalactic medium (IGM) as it is reionized by photons emitted by stars and quasars. The process of reionization heats the IGM and leaves a significant background of ionizing radiation --- both of which inhibit the formation of low mass galaxies. Both of these effects are then accounted for within the galaxy formation model of Cole et al. (2000), producing a fully self-consistent model for the evolution of the IGM and the galaxy population. The resulting model provides a highly flexible framework for exploring the interplay between galaxy formation and the evolution of the IGM and also incorporates a much more accurate treatment of satellite galaxy evolution than has previously been possible in semi-analytic modelling. I use this model to explore the processes of reionization, and assess how the the star formation history of the Universe is affected by reionization. I will then explain in detail the consequences for the population of galaxies at z=0, and focus on the galaxies seen in the Local Group, addressing the question of whether Cold Dark Matter models are in conflict with the abundance of Local Group galaxies.