The Origin of Molecular Cloud Turbulence
ICREA/ICCUB, Barcelona, ES
|Turbulence is ubiquitous in molecular clouds (MCs), but its origin is still unclear because MCs are usually assumed to live longer than the turbulence dissipation time. Interstellar medium (ISM) turbulence is likely driven by SN explosions, but it has never been demonstrated that SN explosions can establish and maintain a turbulent cascade inside MCs consistent with the observations. We have carried out a simulation of SN-driven turbulence in a volume of (250 pc)3, specifically designed to test if SN driving alone can be responsible for the observed turbulence inside MCs. We find that SN driving establishes a global velocity scaling consistent with the usual scaling laws of supersonic turbulence. We also find the same scaling laws extend to the interior of MCs, and their normalization is consistent with the observations, as shown by the velocity-size relation of the MCs selected from the simulation. Other cloud properties, such as mass and size probability distributions, mass-size relation, virial parameters, etc., are found to be consistent with those of observed MCs. Thus, we suggest that MC turbulence originates from the general SN-driven ISM turbulence.
|Caption: Velocity-size relation for the MCs selected from the simulation (blue open circles) and from the Outer Galaxy Survey (red dots). Both the mean values and the scatter are nearly identical between the two samples, each containing 2,241 clouds. The clouds are extracted from the simulation by generating synthetic 12CO maps with a non-LTE radiative transfer code, and analyzing such maps with the same resolution, noise, and cloud selection method as for the observed cloud sample.
M. Juvela, Helsinki U, FI
L. Pan, CfA, US
T. Haugbolle, STARPLAN, DK
A. Nordlund, STARPLAN, DK
Suggested Session: Molecular Clouds