Galaxies are assumed to form by the gravitational collapse of density peaks in an {OMEGA} = 1 universe dominated by cold dark matter. Protogalaxies are torqued up by tidal interactions with the surrounding density field. The rms specific angular momentum acquired through tidal torques has the form h proportional to M^4/3^ around a density peak. The dimensionless angular momentum parameter λ has the value λ = 0.09 for a 3 σ density peak on the scale 10^9^ M_sun_ and is weakly anticorrelated with initial peak height. The baryonic portion of the collapsed structures are able to cool efficiently through bremsstrahlung. If the dissipating baryons form a rotationally supported disk, adiabatically compressing the surrounding dark matter, then the resulting structures have flat rotation curves. A 3 σ peak on a mass scale of 10^9^ M_sun_ has a rotation velocity of ~220 km s^-1^ after dissipation; the baryonic component is dynamically dominant at radii less than ~4 kpc.
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Barbara Ryden (1988) studied this question.