  I present a model for the star formation properties of z~2 starburst
galaxies. Here, I discuss models for the formation of high-z Submillimeter
Galaxies, as well as the CO-H2 conversion factor for these systems. I then
apply these models to literature observations. I show that when using a
functional form for XCO that varies smoothly with the physical properties in
galaxies, galaxies at both local and high-z lie on a unimodal Kennicutt-Schmidt
star formation law, with power-law index of ~2. The inferred gas fractions of
these galaxies are large (fgas ~ 0.2-0.4), though a factor ~2 lower than most
literature estimates that utilize locally-calibrated CO-H2 conversion factors.
