We use cosmological smoothed-particle hydrodynamics (SPH) simulations of the Λ cold dark matter (CDM) model to study the abundance of damped Lyman-α absorbers (DLAs) in the redshift range z = 0 − 4.5. We compute the cumulative DLA abundance by using the relation between DLA cross-section and the total halo mass inferred from the simulations. Our approach includes standard radiative cooling and heating with a uniform UV background, star formation, supernova feedback, as well as a phenomenological model for feedback by galactic winds. The latter allows us to examine, in particular, the effect of galactic outflows on the abundance of DLAs. We employ the “conservative entropy ” formulation of SPH developed by Springel & Hernquist (2002), which mitigates against the systematic overcooling that affected earlier simulations. In addition, we utilise a series of simulations of varying box-size and particle number to isolate the impact of numerical resolution on our results. We show that the DLA abundance was overestimated in previous studies for three reasons: (1) the overcooling of gas occurring with non-conservative formulations o
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