Bosch, Frank denAbel, TomHernquist, Lars2019-09-202003Bosch, F. C. van den, T. Abel, and L. Hernquist. 2003. “The Angular Momentum of Gas in Protogalaxies -- II. The Impact of Pre-Heating.” Monthly Notices of the Royal Astronomical Society 346 (1): 177–85. https://doi.org/10.1046/j.1365-2966.2003.07079.x.0035-87111365-2966http://nrs.harvard.edu/urn-3:HUL.InstRepos:41381695We examine the effect of pre-heating of the intergalactic medium on galaxy formation using cosmological hydrodynamical simulations. By performing simulations both with and without a simple model for pre-heating, we analyse and compare the angular momentum distributions of the dark matter and the baryons. Pre-heating 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 pre-heating, 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 pre-heating decreases (increases) the mass fraction with low (negative) specific angular momentum. We discuss the implications of these findings for the formation of disc galaxies in a pre-heated intergalactic medium, and compare our results to the predictions of Maller & Dekel, who propose an alternative interpretation for the origin of the angular momentum of (proto)galaxies.en-USJournal Article2019-09-2010.1046/j.1365-2966.2003.07079.x