  We examine the effect of preheating of the intergalactic medium on galaxy
formation using cosmological hydrodynamical simulations. By performing
simulations both with and without a simple model for preheating, we analyse and
compare the angular momentum distributions of the dark matter and the baryons.
Preheating unbinds baryons from their dark matter haloes, yielding a baryonic
mass fraction that declines with decreasing halo mass. In addition, the spin
parameter of the gas is reduced with respect to the case without preheating,
while the misalignment between the angular momentum directions of the gas and
dark matter increases strongly. The angular momentum distributions of
individual haloes reveal that preheating decreases (increases) the mass
fraction with low (negative) specific angular momentum. We discuss the
implications of these findings for the formation of disk galaxies in a
preheated intergalactic medium, and compare our results to the predictions of
Maller & Dekel (2002), who propose an alternative interpretation for the origin
of the angular momentum of (proto)-galaxies.
