Internal kinematics of isolated modelled disc galaxies

We present a systematic investigation of rotation curves (RCs) of fully hydrodynamically simulated galaxies, including cooling, star formation with associated feedback, and galactic winds. Applying two commonly used fitting formulae to characterize the RCs, we investigated systematic effects on the shape of RCs by both the observational constraints and internal properties of the galaxies. We mainly focused on effects that occur in measurements of intermediate and high redshift galaxies. We found that RC parameters are affected by the observational setup, like slit misalignment or the spatial resolution and that they also depend on the evolution of a galaxy. Therefore, a direct comparison of quantities derived from measured RCs with predictions of semi-analytic models is difficult. The virial velocity V c , which is usually calculated and used by semi-analytic models, can differ significantly from fit parameters like V max or V opt inferred from RCs. We found that V c is usually lower than typical characteristic velocities derived from RCs. V max alone is in general not a robust estimator of the virial mass.