How the First Stars Regulated Local Star Formation. I. Radiative Feedback

We present numerical simulations of how a 120 M_⊙ primordial star regulates star formation in nearby cosmological halos at z ~ 20 by photoevaporation. Our models include nine-species primordial chemistry and self-consistent multifrequency conservative transfer of UV photons with all relevant radiative processes. Whether or not new stars form in halos clustered around a Population III star ultimately depends on their core densities and proximity to the star. Diffuse halos with central densities below 2-3 cm^-3 are completely ionized and evaporated anywhere in the cluster. Evolved halos with core densities above 2000 cm^-3 are impervious to both ionizing and Lyman-Werner flux at most distances from the star and collapse as quickly as they would in its absence. Star formation in halos of intermediate density can be either promoted or suppressed depending on how the ionization front (I-front) remnant shock compresses, deforms, and enriches the core with H₂. We find that the 120 M_⊙ star photodissociates H₂ in most halos in the cluster, but that catalysis by H^- restores it a few hundred kiloyears after the death of the star, with little effect on star formation. Our models exhibit significant departures from previous one-dimensional, spherically symmetric simulations, which are prone to serious errors due to unphysical geometric focusing effects.