Multi-phase turbulent ISM: Theory Confronting Observations
Guang-Xing Li, MPIR Bonn
Advisor: Nicolas Peretto,
CEA Saclay, Patrick Hennebelle, ENS Paris
Abstract: In this document, we report our recent study on the turbulence inside the
multi-phase ISM. First, we quantify the turbulence inside the molecular
phase ISM by adopting a pixel-by-pixel line fitting strategy and studying
the statistics of the fittings results of the
13CO lines. The histogram of
the
13CO line amplitude and
13CO line FWHM show power-law behavior,
indicative of turbulence. Especially, the histogram of the FWHM of the
13CO line show a dN/dv proportional to v
-2.45 at high velocity end, which seems to
be universal. By plotting the 2D histogram of the
13CO line strength
versus the
13CO line width, a lower limit of the
13CO line width for a
given
13CO line strength can be identified. We argue that such a lower
limit is due to the self-gravity of the molecular cloud. Second, with the
combination of
13CO data from the GRS survey and the Hi 21cm data
from the VGPS survey, we study the connection between the molecular gas
probed with the
13CO line emission and the cold Hi gas probed by the Hi
21cm self-absorption feature. We found that the Hi gas that is associated
with the molecular clouds is also turbulent. The molecular clouds that
have detectable Hi envelope are more turbulent than clouds that do not
show such envelope. Our results support the idea the molecular cloud
turbulence is driven from outside, e.g. by the large-scale converging flow.
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