Probing the Turbulence Dissipation Range and Magnetic Field Strengths in Molecular Clouds. II. Directly Probing the Ion-neutral Decoupling Scale. (arXiv:1901.06289v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Tang_K/0/1/0/all/0/1">Kwok Sun Tang</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Li_H/0/1/0/all/0/1">Hua-Bai Li</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lee_W/0/1/0/all/0/1">Wing-Kit Lee</a>
The linewidth of ions has been observed to be systematically narrower than
that of the coexisting neutrals in molecular clouds (Houde et al. 2000) and
been interpreted as the signature of the decoupling of the neutral turbulence
from magnetic fields in partially ionized medium (Li & Houde 2008; Paper I,
hereafter). As a sequel of Paper I, here we present further observational
evidence that lend support to these earlier proposals with the velocity
coordinate spectrum analysis (Lazarian & Pogosyan 2006). We recover the
turbulent energy spectra of HCN and HCO+(4-3) in a starless molecular filament
in NGC 6334 where magnetic fields play a dynamically important role (Li et al.
2015). Our analysis showed that the neutral spectrum is consistent with
Kolmogorov-type (k^-5/3, where k is the wave number), while that of the ions is
the same on the large scale but steeper (k^-2) for scales smaller than 0.404pc.
We carefully ruled out the possibilities that the spectrum difference can stem
from the differences of ion and neutral optical depth and hyper-fine
structures.
The linewidth of ions has been observed to be systematically narrower than
that of the coexisting neutrals in molecular clouds (Houde et al. 2000) and
been interpreted as the signature of the decoupling of the neutral turbulence
from magnetic fields in partially ionized medium (Li & Houde 2008; Paper I,
hereafter). As a sequel of Paper I, here we present further observational
evidence that lend support to these earlier proposals with the velocity
coordinate spectrum analysis (Lazarian & Pogosyan 2006). We recover the
turbulent energy spectra of HCN and HCO+(4-3) in a starless molecular filament
in NGC 6334 where magnetic fields play a dynamically important role (Li et al.
2015). Our analysis showed that the neutral spectrum is consistent with
Kolmogorov-type (k^-5/3, where k is the wave number), while that of the ions is
the same on the large scale but steeper (k^-2) for scales smaller than 0.404pc.
We carefully ruled out the possibilities that the spectrum difference can stem
from the differences of ion and neutral optical depth and hyper-fine
structures.
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