Recent Progress in Theory of Interstellar Medium and Star Formation

Shu-ichiro Inutsuka (Dept. of Physics, Nagoya Univ.)

I review the recent progress in our theoretical understanding of the physics of
interstellar medium and star formation process.  I emphasize the importance of
the studies for molecular cloud formation that clarifies the controversial
scenarios of star formation and requires our understanding of multiphase
dynamics of interstellar medium in galaxies. One of the highlight of star
formation study is 3D resistive MHD simulation of the self-gravitational
collapse of molecular cloud cores all the way down to the formation of
protostars that covers more than 18 orders of magnitude in density and 7 orders
of magnitude in length scale.  The result of the protostellar collapse
calculation shows two distinct MHD outflows emanating from two different stages
of the central object (the first core and second core), which effectively
solves the angular momentum problem and magnetic flux problem in star formation.
Further calculations include the formation and evolution of protoplanetary disks.
This "top-down" approach for star formation modelling may provide realistic
initial conditions for a "hybrid scenario" of planet formation.