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The kinematics of damped Lyman alpha absorbers (DLAs) are difficult toreproduce in hierarchical galaxy formation models, particularly thepreponderance of wide systems. We investigate DLA kinematics at z=3 usinghigh-resolution cosmological hydrodynamical simulations that include aheuristic model for galactic outflows. Without outflows, our simulations failto yield enough wide DLAs, as in previous studies. With outflows, predicted DLAkinematics are in much better agreement with observations. Comparing twooutflow models, we find that a model based on momentum-driven wind scalingsprovides the best match to the observed DLA kinematic statistics of Prochaska &Wolfe. In this model, DLAs typically arise a few kpc away from galaxies thatwould be identified in emission. Narrow DLAs can arise from any halo and galaxymass, but wide ones only arise in halos with mass >10^11 Mo, from either largecentral or small satellite galaxies. This implies that the success of thisoutflow model originates from being most efficient at pushing gas out fromsmall satellite galaxies living in larger halos. This increases thecross-section for large halos relative to smaller ones, thereby yielding widerkinematics. Our simulations do not include radiative transfer effects ordetailed metal tracking, and outflows are modeled heuristically, but theystrongly suggest that galactic outflows are central to understanding DLAkinematics. An interesting consequence is that DLA kinematics may placeconstraints on the nature and efficiency of gas ejection from high-z galaxies.

Galactic outflows and the kinematics of damped Lyman alpha absorbers