  In the standard picture of disc galaxy formation, baryons and dark matter
receive the same tidal torques, and therefore approximately the same initial
specific angular momentum. However, observations indicate that disc galaxies
typically have only about half as much specific angular momentum as their dark
matter haloes. We argue this does not necessarily imply that baryons lose this
much specific angular momentum as they form galaxies. It may instead indicate
that galaxies are most directly related to the inner regions of their host
haloes, as may be expected in a scenario where baryons in the inner parts of
haloes collapse first. A limiting case is examined under the idealised
assumption of perfect angular momentum conservation. Namely, we determine the
density contrast Delta, with respect to the critical density of the Universe,
by which dark matter haloes need to be defined in order to have the same
average specific angular momentum as the galaxies they host. Under the
assumption that galaxies are related to haloes via their characteristic
rotation velocities, the necessary Delta is ~600. This Delta corresponds to an
average halo radius and mass which are ~60% and ~75%, respectively, of the
virial values (i.e., for Delta = 200). We refer to this radius as the radius of
baryonic collapse R_BC, since if specific angular momentum is conserved
perfectly, baryons would come from within it. It is not likely a simple step
function due to the complex gastrophysics involved, therefore we regard it as
an effective radius. In summary, the difference between the predicted initial
and the observed final specific angular momentum of galaxies, which is
conventionally attributed solely to angular momentum loss, can more naturally
be explained by a preference for collapse of baryons within R_BC, with possibly
some later angular momentum transfer.
