Numerical and Analytical Modelling of Galaxy Formation and Evolution

Original · EN

We review recent developments in theoretical studies of galaxy formation and evolution. In combination with new data from HST, Keck and other large telescopes, numerical and semi-analytic modelling is beginning to build up a coherent picture of galaxy formation. We summarize the current status of modelling of various galactic properties such as the structure of dark matter halos, the galaxy luminosity function, the Tully-Fisher relation, the colour-magnitude relation for ellipticals, the gross morphological properties of galaxies and the counts of faint galaxies as a function of magnitude, redshift and morphology. Many of these properties can be explained, at least at some level, within a broad class of CDM cosmologies, but a number of fundamental issues remain unresolved. We use our semi-analytic model of galaxy formation to interpret the evolutionary status of the Lyman-break galaxies at z≃ 3-3.5 recently discovered by Steidel et al. The abundance and global properties of these objects are compatible with model predictions in a variety of CDM cosmologies, including the standard version. All these models predict mild evolution in the distribution of star formation rates which peaks at around z≃ 1, but is never much larger than it is at present. The Steidel et al. Lyman-break galaxies are among the very first objects in which appreciable star formation is taking place; they thus signal the onset of galaxy formation. We present three example evolutionary histories of Lyman-break galaxies which illustrate that these objects are the precursors of present day, normal, bright ellipticals and spirals.