Shape and Spin of Minihaloes: From Large Scales to the Centres
  The spin and shape of galaxies at the present day have been well-studied both
observationally and theoretically. At high redshifts, however, we have to rely
on numerical simulations. In this study, we investigate the shape and spin of
minihaloes with masses of $M \sim 10^5$--$10^7 \, {\rm M_{\odot}}$ which are of
particular interest as they are the sites where the first stars in the Universe
form. We analyse a large sample of these minihaloes, selected from a high
resolution cosmological simulation. The first minihaloes form at $z \simeq 24$
and by the end of the simulation at $z \simeq 14$ our sample includes $\sim
9000$ minihaloes. We find that the spin parameter of the minihaloes follows a
log-normal distribution with minimal dependence on redshift. Most minihaloes
are prolate, but those formed at the highest redshifts are more prolate than
those formed at lower redshifts. On the scale of the virial radius, there is a
good correlation between the shape and spin of the gas and that of the dark
matter. However, this correlation breaks down in gas which is cooling and
undergoing gravitational collapse. We show, contrary to previous assumptions,
that although the direction of the spin of the central dense gas correlates
well with that of the halo, the magnitude of the spin of the dense gas is
uncorrelated with that of the halo. Therefore, measurements of the spin of
minihaloes on large scales tell us little about the angular momentum of the gas
responsible for forming the first stars.
