Speaker
Prof.
Shu-ichiro Inutsuka
Description
Magnetohydrodynamics of interstellar medium is remarkably different
from that of simple barotropic gas owing to the phase transitions
between cold phase and warm phase (and hot phase) that trigger
variety of instabilities. Identifications of distinct instabilities in various
stages provide us important clues for understanding the saturation
levels of turbulent energies and rates of formation and destruction of
cold clouds, such as HI clouds and molecular clouds. Recent high-
resolution magneto-hydrodynamical simulations of phase transition
dynamics with cooling/heating and thermal conduction have shown that
the formation of molecular clouds requires multiple episodes of
supersonic compression. This finding enables us to create a new
scenario of molecular cloud formation as the interacting shells or
bubbles in galactic scale, which explains many observational properties
such cloud-to-cloud velocity dispersions, accelerating star formation,
and very low star formation efficiencies in filamentary molecular clouds.
We estimate the ensemble-averaged growth rate of individual
molecular clouds, and predict the associated cloud mass function.
Cloud-cloud collisions as a mechanism for forming massive stars and
star clusters can be naturally accommodated in this scenario. This
explains why massive stars formed in cloud-cloud collisions follows the
power-law slope of the mass function of molecular cloud cores
repeatedly found in low-mass star forming regions.
Primary author
Prof.
Shu-ichiro Inutsuka