The fragmentation of pre-enriched primordial objects

摘要: Recent theoretical investigations have suggested that the formation of very first stars, forming out metal-free gas, was fundamentally different from present-day case. The question then arises which effect responsible for this transition in star properties. In paper, we study metallicity on evolution gas a collapsing dark matter mini-halo. We model such system as an isolated 3σ peak mass collapses at , using smoothed particle hydrodynamics. has supposed level pre-enrichment either or 10−3 Z⊙. assume H2 been radiatively destroyed by presence soft UV background. Metals therefore provide only viable cooling temperatures below 104 K. find proceeds differently two cases. lower simulation fails to undergo continued collapse and fragmentation, whereas higher case dissipatively settles into centre halo. central characterized densities temperature, closely follows cosmic microwave background, is gravitationally unstable undergoes vigorous fragmentation. discuss physical reason existence critical metallicity, its possible dependence redshift. Compared with pure H/He case, fragmentation leads larger relative number low-mass clumps.