The First Compact Objects in the Λ-dominated Universe

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We calculate the evolution of a low-mass (M ≤ 10⁵ M) spherically symmetric density perturbation in the Ωb h²=0.02, Ωₘ =0.35, ΩΛ=0.65, h=0.72 Universe. The results are compared with the ones that assume no cosmological constant and the flat, dark matter dominated Universe. We include thermal processes and non-equilibrium chemical evolution of the collapsing gas. We find that direct formation of bound objects with such masses by z=8 is unlikely so in fact they may form only through fragmentation of greater objects. This is in stark contrast to the Ω=1 pure CDM cosmology, where low-mass objects form abundantly at redshits z>10.