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The structure of a sample of high-redshift (z=2), rotating galaxies with highstar formation rates and turbulent gas velocities of sigma=40-80 km/s isinvestigated. Fitting the observed disk rotational velocities and radii with aMo, Mao, White (1998) (MMW) model requires unusually large disk spin parameterslambda_d>0.1 and disk-to-dark halo mass fraction m_d=0.2, close to the cosmicbaryon fraction. The galaxies segregate into dispersion-dominated systems with1<vmax/sigma<3, maximum rotational velocities vmax<200 km/s and disk half-lightradii rd=1-3 kpc and rotation-dominated systems with vmax>200 km/s,vmax/sigma>3 and rd=4-8 kpc. For the dispersion-dominated sample, radialpressure gradients partly compensate the gravitational force, reducing therotational velocities. Including this pressure effect in the MMW model,dispersion-dominated galaxies can be fitted well with spin parameters lflambda_d=0.03-0.05 for high disk mass fractions of m_d=0.2 and withlambda_d=0.01-0.03 for m_d=0.05. These values are in good agreement withcosmological expectations. For the rotation-dominated sample however pressureeffects are small and better agreement with theoretically expected disk spinparameters can only be achieved if the dark halo mass contribution in thevisible disk regime (2-3*rd) is smaller than predicted by the MMW model. Weargue that these galaxies can still be embedded in standard cold dark matterhalos if the halos did not contract adiabatically in response to diskformation. It is shown that the observed high turbulent gas motions of thegalaxies are consistent with a Toomre instability parameter Q=1 which is equalto the critical value, expected for gravitational disk instability to be themajor driver of turbulence. The dominant energy source of turbulence is thenthe potential energy of the gas in the disk.

High-Redshift Star-Forming Galaxies: Angular Momentum and Baryon Fraction, Turbulent Pressure Effects and the Origin of Turbulence