  The efficiency of star formation governs many observable properties of the
cosmological galaxy population, yet many current models of galaxy formation
largely ignore the important physics of star formation and the interstellar
medium (ISM). Using hydrodynamical simulations of disk galaxies that include a
treatment of the molecular ISM and star formation in molecular clouds
(Robertson & Kravtsov 2008), we study the influence of star formation
efficiency and molecular hydrogen abundance on the properties of high-redshift
galaxy populations. In this work, we focus on a model of low-mass, star forming
galaxies at 1<~z<~2 that may host long duration gamma-ray bursts (GRBs).
Observations of GRB hosts have revealed a population of faint systems with star
formation properties that often differ from Lyman-break galaxies (LBGs) and
more luminous high-redshift field galaxies. Observed GRB sightlines are
deficient in molecular hydrogen, but it is unclear to what degree this
deficiency owes to intrinsic properties of the galaxy or the impact the GRB has
on its environment. We find that hydrodynamical simulations of low-stellar mass
systems at high-redshifts can reproduce the observed star formation rates and
efficiencies of GRB host galaxies at redshifts 1<~z<~2. We show that the
compact structure of low-mass high-redshift GRB hosts may lead to a molecular
ISM fraction of a few tenths, well above that observed in individual GRB
sightlines. However, the star formation rates of observed GRB host galaxies
imply molecular gas masses of 10^8 - 10^9 M_sun similar to those produced in
the simulations, and may therefore imply fairly large average H_2 fractions in
their ISM.
