Shuo Kong
When
Magnetically Regulated Molecular Cloud and Star Formation
Abstract:
We have investigated the possibility of molecular cloud formation
in a magnetically dominating regime. Two atomic gas clouds with
typical conditions of the cold neutral medium (CNM) were set to
collide at the interface of reverse magnetic fields. The collision
triggered magnetic reconnection which produced a 20 pc filamentary cloud.
The cloud, with rich fiber-like sub-structures, developed a fully molecular
spine by the end of the simulation at 5 Myr. Radiative transfer modeling
of dust emission at far infrared wavelength showed dense cores along the
filament. Some of the cores host one to a few sinks and the sinks
scattered over a span of 5 pc in the middle part of the filament. No
obvious signs of sink clustering were observed because the filament,
with widespread dense gas, did not undergo a global collapse. A zoom-in
view of the central filament showed that the sink-hosting cores typically
exhibited connecting fibers in dust emission and high-velocity gas in CO
line emission, indicative of active accretion through streamers.
Supersonic turbulence in the filament had a magnetic origin
due to the magnetic transportation at a trans-Alfv\'enic speed.
Our investigation has shown that filamentary molecular cloud
can form in a magnetically dominating regime without the need of gravity.
The filamentary cloud, with typical physical properties seen in observations,
is naturally wrapped by a helical magnetic field which should show up
as reverse magnetic fields on two sides from most viewing angles.