Mass-metallicity relation from z=5 to the present: evidence for a transition in the mode of galaxy growth at z=2.6 due to the end of sustained primordial gas infall

We analyse the redshift evolution of the mass-metallicity relation in a sample of 110 Damped Lyman alpha absorbers (DLAs) spanning the redshift range z = 0.11-5.06 and find that the zero-point of the correlation changes significantly with redshift. The evolution is such that the zero-point is constant at the early phases of galaxy growth (i.e. no evolution) but then features a sharp break at z = 2.6 +/- 0.2 with a rapid incline towards lower redshifts such that damped absorbers of identical masses are more metal rich at later times than earlier. The slope of this mass-metallicity correlation evolution is 0.35 +/- 0.07 dex per unit redshift. We compare this result to similar studies of the redshift evolution of emission selected galaxy samples and find a remarkable agreement with the slope of the evolution of galaxies of stellar mass log(M-*/M-circle dot) approximate to 8.5. This allows us to form an observational tie between damped absorbers and galaxies seen in emission. We use results from simulations to infer the virial mass of the dark matter halo of a typical DLA galaxy and find a ratio (M-vir/M-*) approximate to 30. We compare our results to those of several other studies that have reported strong transition-like events at redshifts around z = 2.5-2.6 and argue that all those observations can be understood as the consequence of a transition from a situation where galaxies were fed more unprocessed infalling gas than they could easily consume to one where they suddenly become infall starved and turn to mainly processing, or re-processing, of previously acquired gas.