Formation of the First Low-Mass Stars from Cosmological Initial
  Conditions
  We simulate the formation of a metal-poor (10^-2 Zsun) stellar cluster in one
of the first galaxies to form in the early Universe, specifically a
high-redshift atomic cooling halo (z~14). This is the first calculation that
resolves the formation of individual metal-enriched stars in simulations
starting from realistic cosmological initial conditions. We follow the
evolution of a single dense clump among several in the parent halo. The clump
forms a cluster of ~40 stars and sub-stellar objects within 7000 years and
could continue forming stars ~5 times longer. Protostellar dust heating has a
negligible effect on the star formation efficiency, at least during the early
evolutionary stages, but it moderately suppresses gaseous fragmentation and
brown dwarf formation. We observe fragmentation in thin gaseous filaments and
sustained accretion in larger, rotating structures as well as ejections by
binary interactions. The stellar initial mass function above 0.1 Msun,
evaluated after ~10^4 years of fragmentation and accretion, seems in agreement
with the recent measurement in ultra-faint dwarf spheroidal Galactic satellites
of Geha et al. (2013).
