  [abridged]We use 3D cosmological simulations with radiative transfer to study
the formation and evolution of the first galaxies in a LCDM cosmology. We find
that the first luminous objects ("small-halos") are characterized by a bursting
star formation (SF) that is self-regulated by a feedback process acting on
cosmological instead of galactic scales. The global star formation history is
regulated by the mean number of ionizing photons that escape from each source,
\epsilon_{UV}\fesc. It is almost independent of the assumed star formation
efficiency parameter, \epsilon_*, and the intensity of the dissociating
background. The main feedback process that regulates the SF is the re-formation
of H_2 in front of HII regions and inside relic HII regions. The HII regions
remain confined inside filaments, maximizing the production of H_2 in overdense
regions through cyclic destruction/reformation of H_2. If \epsilon_{UV}\fesc >
10^{-8}/\epsilon_* the SF is self-regulated, photo-evaporation of "small-halo"
objects dominate the metal pollution of the low density IGM, and the mass of
produced metals depends only on \fesc. If \epsilon_{UV}\fesc \simlt
10^{-8}/\epsilon_*, positive feedback dominates, and "small-halo" objects
constitute the bulk of the mass in stars and metals at least until redshift z
\sim 10. "Small-halo" objects cannot reionize the universe because the feedback
mechanism confines the HII regions inside the large scale structure filaments.
In contrast to massive objects, which can reionize voids, "small-halo" objects
partially ionize only the dense filaments while leaving the voids mostly
neutral.
