After this efficient formation, most of the gas is not in favorable conditions for star formation. Indeed, larger potential wells have not formed yet, and the density threshold is not reached. It is therefore likely that the gas will slowly accumulate in bigger potentials to form galaxies, as sketched in fig. 3. In the inner parts of these early galaxies, star formation can then begin. Then galaxy interactions will stirr and heat the gas through shocks and gravitational perturbations.
Besides, interactions accelerate the angular momentum transfer: part of the HI gas is dragged outwards in tails. Most of the gas is driven inwards, giving rise to huge nuclear starbursts (and may be AGN). Galaxy evolution is highly accelerated. The cold gas that was settled around each galaxy is heated and virialised in the new common potential and might be visible through X-rays.