  We compare the metallicity distribution of Galactic Halo stars with 3D
realizations of hierarchical galaxy formation. Outflows from dwarf galaxies
enrich the intergalactic medium inhomogeneously, at a rate depending on the
local galaxy density. Consequently, the first stars created in small
early-forming galaxies are less metal-rich that the first stars formed in more
massive galaxies which typically form later. As most halo stars are likely to
originate in accreted dwarfs, while disk stars formed out of outflow-enriched
gas, this scenario naturally generates a ``metallicity floor'' for old disk
stars, which we find to be roughly coincident with the higher end of our
predicted metallicity distribution of halo stars, in agreement with
observations. The broad and centrally peaked distribution of halo star
metallicities is well reproduced in our models, with a natural dispersion
depending on the exact accretion history. Our modeling includes the important
``baryonic stripping'' effect of early outflows, which brush away the tenuously
held gas in neighboring pre-virialized density perturbations. This stripping
process does not significantly modify the predicted shape of the halo star
metal distribution but inhibits star-formation and hence the number of accreted
stars, helping to reproduce the observed total Galactic halo luminosity and
also the lack of low-luminosity local dwarf galaxies relative to N-body
predictions.
