The end of the dark ages in modified Newtonian dynamics

We study the evolution of a spherically symmetric density perturbation in the Modified Newtonian Dynamics model applied to the net acceleration over Hubble flow. The background cosmological model is a Λ-dominated, low-Ωb Friedmann model with no cold dark matter. We include thermal processes and non-equilibrium chemical evolution of the collapsing gas. We find that under these assumptions the first low-mass objects (M≤ 3 × 104M⊙) may collapse already for z~ 30, which is in quite good agreement with the recent Wilkinson Microwave Anisotropy Probe results. A lower value of a0 would lead to much slower collapse of such objects.