The Dependence of the Galactic Star Formation Laws on Metallicity
  We describe results from semi-analytical modelling of star formation in
protocluster clumps of different metallicities. In this model, gravitationally
bound cores form uniformly in the clump following a prescribed core formation
efficiency per unit time. After a contraction timescale which is equal to a few
times their free-fall times, the cores collapse into stars and populate the
IMF. Feedback from the newly formed OB stars is taken into account in the form
of stellar winds. When the ratio of the effective energy of the winds to the
gravitational energy of the system reaches unity, gas is removed from the clump
and core and star formation are quenched. The power of the radiation driven
winds has a strong dependence on metallicity and it increases with increasing
metallicity. Thus, winds from stars in the high metallicity models lead to a
rapid evacuation of the gas from the protocluster clump and to a reduced star
formation efficiency, as compared to their low metallicity counterparts. We
derive the metallicity dependent star formation efficiency per unit time in
this model as a function of the gas surface density Sigma_g. This is combined
with the molecular gas fraction in order to derive the dependence of the
surface density of star formation Sigma_SFR on Sigma_g. This feedback regulated
model of star formation reproduces very well the observed star formation laws
in galaxies extending from low gas surface densities up to the starburst
regime. Furthermore, the results show a dependence of Sigma_SFR on metallicity
over the entire range of gas surface densities, and can also explain part of
the scatter in the observations.
