Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-10-22
Astronomy and Astrophysics
Astrophysics
12 Pages, 9 Figures, accepted to ApJ, printing in colour recommended
Scientific paper
10.1086/589136
The median observed velocity width v_90 of low-ionization species in damped Ly-alpha systems is close to 90 km/s, with approximately 10% of all systems showing v_90 > 210 km/s at z=3. We show that a relative shortage of such high-velocity neutral gas absorbers in state-of-the-art galaxy formation models is a fundamental problem, present both in grid-based and particle-based numerical simulations. Using a series of numerical simulations of varying resolution and box size to cover a wide range of halo masses, we demonstrate that energy from gravitational infall alone is insufficient to produce the velocity dispersion observed in damped Ly-alpha systems, nor does this dispersion arise from an implementation of star formation and feedback in our highest resolution (~ 45 pc) models, if we do not put any galactic winds into our models by hand. We argue that these numerical experiments highlight the need to separate dynamics of different components of the multiphase interstellar medium at z=3.
Norman Michael L.
Prochaska Jason Xavier
Razoumov Alexei Olegovich
Sommer-Larsen Jesper
Wolfe Arthur M.
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