The Tully-Fisher relation and its evolution with redshift in cosmological simulations of disc galaxy formation

We present predictions on the evolution of the Tully-Fisher (TF) relation with redshift, based on cosmological N-body/hydrodynamical simulations of disc galaxy formation and evolution. The simulations invoke star formation and stellar feedback, chemical evolution with non-instantaneous recycling, metallicity-dependent radiative cooling and effects of a metagalactic ultraviolet field, including simplified radiative transfer. At z = 0, the simulated and empirical TF relations are offset by about 0.4 mag (1 sigma) in the B and I bands. The origin of these offsets is somewhat unclear, but it may not necessarily be a problem of the simulations only. As to evolution, we find a brightening of the TF relation between z = 0 and 1 of about 0.85 mag in rest-frame B band, with a non-evolving slope. The brightening we predict is intermediate between the (still quite discrepant) observational estimates. This evolution is primarily a luminosity effect, while the stellar mass TF relation shows negligible evolution. The individual galaxies do gain stellar mass between z = 1 and 0, by a 50-100 per cent, but they also correspondingly increase their characteristic circular speed. As a consequence, individually they mainly evolve along the stellar mass TF relation, while the relation as such does not show any significant evolution.