Models of disk evolution: Confrontation with observations

We present simple models for disk evolution based on two different approaches: a forward approach based on predictions generic to hierarchical models for structure formation and a backward approach based on detailed modeling of the Milky Way. We normalize these models to local observations and predict high-redshift luminosities, sizes, circular velocities, and surface brightnesses. Both approaches yield somewhat similar predictions for size, surface brightness, and luminosity evolution, although they clearly differ in the amount of number evolution. These predictions seem to be broadly consistent with the high-redshift observations of Simard et al., suggesting that the B-band surface brightness of disks has indeed evolved by similar to1.5 mag from z similar to 0 to z similar to 1, similar to what is seen in the models, and is not an artifact of selection effects, as previously claimed. We also find a lack of low surface brightness galaxies in several high-redshift samples relative to model predictions based on local samples.