We explore the predictions of the standard hierarchical clustering scenario of galaxy formation , regarding the numbers and metallicities of PopIII stars likely to be found within our Galaxy today .
By PopIII we shall be referring to stars formed at large redshift ( z > 4 ) , with low metallicities ( [ Z / Z _ { \odot } ] < -2.5 ) and in small systems ( total mass \buildrel < \over { \sim } 2 \times 10 ^ { 8 } M _ { \odot } ) that are extremely sensitive to stellar feedback , and which through a prescribed merging history ( Lacey & Cole 1993 ) end up becoming part of the Milky Way today .
An analytic , extended Press-Schechter formalism is used to get the mass functions of halos which will host PopIII stars at a given redshift , and which will end up in Milky Way sized systems today .
Each of these is modeled as a mini galaxy , with a detailed treatment of the dark halo structure , angular momentum distribution , final gas temperature and disk instabilities , all of which determine the fraction of the baryons which are subject to star formation .
Use of new primordial metallicity stellar evolutionary models allows us to trace the history of the stars formed , give accurate estimates of their expected numbers today , and their location in L / L _ { \odot } vs . T / K HR diagrams .
A first comparison with observational data suggests that the IMF of the first stars was increasingly high mass weighted towards high redshifts , levelling off at z \lower 2.15 pt \hbox { $ \buildrel > \over { \sim } $ } 9 at a characteristic stellar mass scale m _ { s } = 10 - 15 M _ { \odot } .