Abstract
ApJ, 769, 74, 2013 We use high-resolution cosmological hydrodynamic simulations to study the
angular momentum acquisition of gaseous halos around Milky Way sized galaxies.
We find that cold mode accreted gas enters a galaxy halo with ~70% more
specific angular momentum than dark matter averaged over cosmic time (though
with a very large dispersion). In fact, we find that all matter has a higher
spin parameter when measured at accretion than when averaged over the entire
halo lifetime, and is well characterized by \lambda~0.1, at accretion. Combined
with the fact that cold flow gas spends a relatively short time (1-2 dynamical
times) in the halo before sinking to the center, this naturally explains why
cold flow halo gas has a specific angular momentum much higher than that of the
halo and often forms "cold flow disks". We demonstrate that the higher angular
momentum of cold flow gas is related to the fact that it tends to be accreted
along filaments.