Galactosynthesis predictions at high redshift

We predict the Tully–Fisher (TF) and surface-brightness–magnitude relations for disc galaxies at z = 3 and discuss the origin of these scaling relations and their scatter. We find that both halo dynamics and the star formation history play important roles, and we show that the variation of the TF relation with redshift can be a potentially powerful discriminator of galaxy-formation models. In particular, the TF relation at high redshift might be used to break parameter degeneracies among galactosynthesis models at z = 0, as well as to constrain the redshift distribution of collapsing dark-matter haloes, the star formation history and baryon fraction in the disc and the distribution of halo spins.