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

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

2009-07-27

arxiv.org/abs/0907.4777v2

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

23 pages, 4 figures, ApJ, in press

Scientific paper

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 1200 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. Including this pressure effect in the MMW model, dispersion-dominated galaxies can be fitted well with spin parameters lf lambda_d=0.03-0.05 for high disk mass fractions of m_d=0.2 and with lambda_d=0.01-0.03 for m_d=0.05. These values are in good agreement with cosmological expectations. For the rotation-dominated sample however pressure effects are small and better agreement with theoretically expected disk spin parameters can only be achieved if the dark halo mass contribution in the visible disk regime (2-3*rd) is smaller than predicted by the MMW model. We argue that these galaxies can still be embedded in standard cold dark matter halos if the halos did not contract adiabatically in response to disk formation. It is shown that the observed high turbulent gas motions of the galaxies are consistent with a Toomre instability parameter Q=1 which is equal to the critical value, expected for gravitational disk instability to be the major driver of turbulence. The dominant energy source of turbulence is then the potential energy of the gas in the disk.

Affiliated with

Also associated with

No associations

Rating

High-Redshift Star-Forming Galaxies: Angular Momentum and Baryon Fraction, Turbulent Pressure Effects and the Origin of Turbulence does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with High-Redshift Star-Forming Galaxies: Angular Momentum and Baryon Fraction, Turbulent Pressure Effects and the Origin of Turbulence, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High-Redshift Star-Forming Galaxies: Angular Momentum and Baryon Fraction, Turbulent Pressure Effects and the Origin of Turbulence will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-681088