  We compute the specific angular momentum distributions of a sample of low
mass disk galaxies observed by Swaters. We compare these distributions to those
of dark matter haloes obtained by Bullock et al. from high resolution N-body
simulations of structure formation in a LCDM Universe. We find that although
the disk mass fractions are significantly smaller than the Universal baryon
fraction, the total specific angular momenta of the disks are in good agreement
with those of dark matter haloes. This suggests that disks form out of only a
small fraction of the available baryons, but yet manage to draw most of the
available angular momentum. In addition we find that the angular momentum
distributions of disks are clearly distinct from those of the dark matter;
disks lack predominantly both low and high specific angular momentum.
Understanding these findings in terms of a coherent picture for disk formation
is challenging. Cooling, feedback and stripping, which are the main mechanisms
to explain the small disk mass fractions found, seem unable to simultaneously
explain the disk's angular momentum distribution. In fact, it seems that the
baryons that make up the disks must have been born out of angular momentum
distributions that are clearly distinct from those of LCDM haloes. Therefore,
understanding the angular momentum content of disk galaxies remains an
important challenge for our picture of galaxy formation.
