EPoS Contribution
EPoS Contribution
Understanding the Formation and Structure of Molecular Clouds

Alexei Kritsuk
UC San Diego, La Jolla, USA
I will present results from a suite of MHD simulations with adaptive mesh refinement exploring the formation and build-up of structure in molecular clouds through the interaction of turbulence, self-gravity, and magnetic fields. Using dimensional analysis, I will show that both linewidth--size and mass--size relations within molecular clouds on scales from 0.1 to 50 pc can be explained by a simple conceptual theory of compressible turbulence with no need to invoke self-gravity. The observed "universal" scaling is perfectly matched by the scaling exponents measured in the simulations. The self-similarity of structure established by the turbulence, however, breaks in star-forming clouds, where the development of gravitational instability in the vicinity of the sonic scale (~0.05 pc) leads to the formation of prestellar cores. One routinely observed signature of gravity is the power-law tail in the (otherwise lognormal) column-density distribution associated with filamentary structures hosting the cores. A very high effective resolution of our simulations (up to 10^6) and an extremely high dynamic range in gas density (over 10^12) allowed us to unambiguously associate the tail with self-similar collapse solutions and predict its power index. Moreover, the observed mass--size correlation for prestellar cores can be explained using the same approach. The simulations allowed us to directly study the three-dimensional structure of converging gas flows within regions similar to those identified as star-forming filaments in recent Herschel observations. I will also discuss magnetization levels that self-consistently develop in turbulent molecular clouds, dense filaments, and prestellar cores through self-organization.
D. Collins, LANL, USA
M.L. Norman, UCSD, USA
S.D. Ustyugov, KIAM, Russia
R. Wagner, SDSC, USA
Key publication