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

Understand

The structure of a sample of high-redshift (z=2), rotating galaxies with high star formation rates and turbulent gas velocities of sigma=40-80 km/s is investigated.

• Fitting the observed disk rotational velocities and radii with a Mo, Mao, White (1998) (MMW) model requires unusually large disk spin parameters lambda_d>0.1 and disk-to-dark halo mass fraction m_d=0.2, close to the cosmic baryon fraction.
• The galaxies segregate into dispersion-dominated systems with 1<vmax/sigma<3, maximum rotational velocities vmax<200 km/s and disk half-light radii 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, radial pressure gradients partly compensate the gravitational force, reducing the rotational velocities.