Abstract
We examine the abundance, clustering and metallicity of Damped Lyman-$\alpha$
Absorbers (DLAs) in hydrodynamic cosmological simulations using the moving mesh
code AREPO. We incorporate models of supernova and AGN feedback, and molecular
hydrogen formation. We compare our simulations to the column density
distribution function at $z=3$, the total DLA abundance at $z=2-4$, the
measured DLA bias at $z=2$ and DLA metallicities at $z=2-4$. Our preferred
models produce populations of DLAs in good agreement with most of these
observations, except the DLA abundance at $z < 3$, which we show requires
stronger feedback in $10^11-12 h^-1 M_ødot$ mass halos. While the DLA
population probes a range of halo masses, we find the cross-section is
dominated by halos of mass $10^10.5 h^-1 M_ødot$ at $z=3$ and $10^11
h^-1 M_ødot$ at $z=2$. Simulations without feedback are in strong tension
with all these observables, indicating a need for strong stellar feedback at
$z=2-4$ independently of the star formation threshold. We demonstrate that DLAs
are a powerful probe of the physical processes that shape galaxy formation, in
particular supernova feedback processes. As DLAs arise from gas at a lower
density than the star formation threshold, the information they provide is
complementary to that contained in the stellar component of galaxies.
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