The Impact of Cooling and Feedback on Disc Galaxies

We present detailed, analytical models for the formation of disc galaxies to investigate the impact that cooling and feedback have on their structural properties. In particular, we investigate which observables extracted directly from the models are best suited as virial mass estimators, and to what extent they allow the recovery of the model input parameters regarding the feedback and cooling efficiencies. Contrary to naive expectations, the luminosities and circular velocities of disc galaxies are extremely poor indicators of total virial mass. Instead, we show that the product of disc scale length and rotation velocity squared yields a much more robust estimate. We show that feedback can cause a narrow correlation between galaxy mass fraction and halo spin parameter, similar to that found recently by van den Bosch, Burkert and Swaters from an analysis of dwarf galaxy rotation curves. Finally we investigate the impact that cooling and feedback have on the colors, metallicities, star formation histories and Tully-Fisher relation of disc galaxies.