  We investigate the nature of the physical structures giving rise to damped
Lyman alpha absorption systems (DLAS) at high redshift. In particular, we
examine the suggestion that rapidly rotating large disks are the only viable
explanation for the characteristic observed asymmetric profiles of low
ionization absorption lines. We demonstrate using hydrodynamic simulations of
galaxy formation in a cosmological context that irregular protogalactic clumps
can reproduce the observed velocity width distribution and asymmetries of the
absorption profiles equally well. The velocity broadening in the simulated
clumps is due to a mixture of rotation, random motions, infall and merging. The
observed velocity width correlates with the virial velocity of the dark matter
halo of the forming protogalactic clump (v_{wid} ~ 0.6 times v_{vir} for the
median values with a large scatter of order a factor two between different
lines-of-sight). The typical virial velocity of the halos required to give rise
to the DLAS population is about 100 km/s and most standard hierarchical
structure formation scenarios can easily account even for the largest observed
velocity widths. We conclude that the evidence that DLAS at high redshift are
related to large rapidly rotating disks with v_circ >= 200 km/s is not
compelling.
