The Effect of Star Formation on the Redshift Evolution of Interstellar
  Metals, Atomic and Molecular Gas in Galaxies
  We examine how the atomic and molecular gas components of galaxies evolve to
higher redshifts using the semi-analytic galaxy formation models of Fu et al.
(2010) in which we track the surface density profiles of gas in disks. We adopt
two different prescriptions based either on gas surface density and
metallicity, or on interstellar pressure, to compute the molecular fraction as
a function of radius in each disk. We demonstrate that the adopted star
formation law determines how the {\em balance} between gas, stars and metals
changes with time in the star-forming galaxy population, but does not influence
the total mass in stars formed into galaxies at redshifts below $z\sim 2.5$.
The redshift evolution of the mass-metallicity relation places strong
constraints on the timescale over which cold gas is converted into stars in
high redshift galaxies, and favours models where this remains constant at
values around 1-2 Gyr. Future observations of the evolution of the average
molecular-to-atomic gas ratio in galaxies as a function of stellar mass and
redshift will constrain models of the atomic-to-molecular transition.
