We investigate the differential effects of metal cooling and galactic stellar winds on the
cosmological formation of individual galaxies with three sets of cosmological,
hydrodynamical zoom simulations of 45 haloes in the mass range 1011< M halo< 1013 M⊙.
Models including both galactic winds and metal cooling (i) suppress early star formation at
z≳ 1 and predict reasonable star formation histories for galaxies in present-day haloes of≲
1012 M⊙,(ii) produce galaxies with high cold gas fractions (30–60 per cent) at high�…

We use a radiation hydrodynamic simulation of the hydrogen reionization epoch to study O i
absorbers at z∼ 6. The intergalactic medium (IGM) is reionized before it is enriched; hence,
O i absorption originates within dark matter haloes. The predicted abundance of O i
absorbers is in reasonable agreement with observations. At z= 10,≈ 70 per cent of
sightlines through atomically cooled haloes encounter a visible (NOi> 1014cm− 2) column.
Reionization ionizes and removes gas from haloes less massive than 108.4 M⊙, but 20 per�…