Rotation rates, sizes and star formation efficiencies of a representative population of simulated disc galaxies

We examine the rotation rates, sizes and star formation (SF) efficiencies of a representative population of simulated disc galaxies extracted from the GalaxiesIntergalactic Medium Interaction Calculation (GIMIC) suite of cosmological hydrodynamic simulations. These simulations include efficient, but energetically feasible supernova feedback, but have not been tuned in any way to produce realistic disc galaxies. Yet, they generate a large number of discs, without requiring extremely high resolution. Over the wide galaxy stellar mass range, 9.0 <= log(10)[M-*(M-circle dot)] < 10.5, the simulations reproduce the observed TullyFisher relation, the rotation curves of disc galaxies in bins of stellar mass, the masssize relation of disc galaxies, the optical rotation to virial circular velocity ratio (V-opt/V-vir) and the SF efficiencies of disc galaxies as inferred from stacked weak lensing and stacked satellite kinematics observations. They also reproduce the specific star formation rates of similar to L-* galaxies but predict too low levels of SF for low-mass galaxies, which is plausibly due to the finite resolution of the simulations. At higher stellar masses, log(10)[M-*(M-circle dot)] > 10.6, the simulated galaxies are too concentrated and have too high SF efficiencies. We conjecture that this shortcoming reflects the neglect of feedback from accreting supermassive black holes in these simulations. We conclude that it is possible to generate a representative population of disc galaxies that reproduces many of the observed trends of local disc galaxies using standard numerical hydrodynamic techniques and a plausible implementation of the subgrid astrophysical processes thought to be relevant to galaxy formation.