Photodissociation feedback of Population III stars \\on their neighbor prestellar cores

Abstract

We investigate the star formation process in primordial environment in the presence of radiative feedback by other population III stars formed earlier. In this paper, we focus our attention on the effects by photodissociative radiation toward the full understanding of the radiative feedback effects. We perform three dimensional radiation hydrodynamics simulations on this issue as well as analytic estimates, paying special attention on the self-shielding effect and dynamics of the star-forming cloud. As a result, we find that the ignition timing of the source star is crucial. If the ignition is later than the epoch when the central density of the collapsing cloud exceeds $\sim 10^3-10^4{\rm cm^{-3}}$, the collapse cannot be reverted, even if the source star is located at $\la$ 100pc. The uncertainty of the critical density comes from the variety of initial conditions of the collapsing cloud. We also find the analytic criteria for a cloud to collapse with given central density, temperature and the Lyman-Werner(LW) band flux which irradiates the cloud. Although we focus on the radiation from neighbor stars, this result can also be applied to the effects of diffuse LW radiation field, that is expected to be built up prior to the reionization of the universe. We find that self-gravitating clouds can easily self-shield from diffuse LW radiation and continue their collapse for densities larger than $\sim 10^3 {\rm cm^{-3}}$.