We (alongside an independent group in Munich [G. Kauffmann et al]) were pioneers in developing a new method of modelling galaxy formation in an evolving cosmological setting. The first papers by both our group and the Munich group were in the early 1990s. Since then the models have become more sophisticated and also many other groups have emulated and improved upon our early work—most notably the group that began in Santa Cruz [R. S. Somerville et al]. The value of our highly cited 2000 paper is that it fully describes and explains all the details of our sophisticated second-generation model. The consequence of this is that it is cited as a place where one can find out about the methodology of these galaxy formation models by us, by most of the other groups that have developed similar models and by observers who compare these models with their data.

The general field of galaxy formation and particularly the observational aspects of galaxy evolution are currently very hot topics. This interest is mainly driven by the technical advances that have led to the construction of powerful 8-m class telescopes capable of studying the galaxy population at high redshift when the universe was only a fraction of its current age. The value of the methods and results described in our paper are that they allow these observations to be interpreted within a theoretical model that not only takes account of the astrophysical processes of cooling condensing gas and star formation but also the accompanying gravitational evolution of the dark matter.

The paper describes a coherent and comprehensive way of modelling how galaxies form in the evolving universe. Our model incorporates a realistic modelling of how the dark matter that dominates the mass of our universe evolves under the influence of gravity. The initially smooth distribution becomes clumpy and the first small clumps coalesce under their mutual gravitational attraction to form ever larger structures. Within this evolving web of dark matter filaments and clusters the primordial gas settles into the densest structures. These are the sites where gas is able to cool and condense turning into stars and starting the process of galaxy formation. We model all these processes and so are able to relate the observed properties of galaxies to what one expects for a given cosmological model. It is in this way that theory and observations are brought face to face.