EPoS Contribution
EPoS Contribution
Turbulence decay and cloud core relaxation

Yang Gao
Tsinghua, Beijing, CN
Turbulence supports molecular cloud cores from evolving to gravitational collapse and hence sets a lower bound on the size of molecular cloud cores in which star formation can occur. On the other hand, without a continuous external energy source maintaining the turbulence, such as in molecular clouds, the turbulence decays with an energy dissipation time comparable to the dynamic timescale of clouds, which could change the size limits obtained from Jean's criterion by assuming constant turbulence intensities. Here we adopt scaling relations of physical variables in decaying turbulence to analyze its specific effects on the formation of stars. We find that the decay of turbulence provides an additional approach for Jean's criterion to be achieved, after which gravitational infall governs the motion of the cloud core. This epoch of turbulence decay is defined as cloud core relaxation. The existence of cloud core relaxation provides a more complete understanding of the effect of the competition between turbulence and gravity on the dynamics of molecular cloud cores and star formation.
Caption: Relaxation time needed for a cloud core embedded in a (giant) molecular cloud of diameter l0=100 pc containing typical initial turbulent motions of u0 = 30, 10, and 3 km/s to become gravitationally unstable.
H. Xu, MPIDS/Tsinghua, DE/CH
C.K. Law, Princeton U/Tsinghua, US/CH
Key publication

Suggested Session: Turbulence