Poidevin, F.; Bastien, P.
Bibliographical reference
The Astrophysical Journal, Volume 650, Issue 2, pp. 945-955.
Advertised on:
10
2006
Journal
Citations
24
Refereed citations
18
Description
New visible polarization data combined with existing IR and FIR
polarization data are used to study how the magnetic field threading the
filamentary molecular cloud GF 9 connects to larger structures in its
general environment. When visible and NIR polarization data are
combined, no evidence is found for a plateau in the polarization above
extinction AV~1.3, as seen in dark clouds in Taurus. This
lack of saturation effect suggests that even in the denser parts of GF 9
magnetic fields can be probed. The visible polarization is smooth and
has a well-defined orientation. In the core region, the IR and FIR data
are also well defined, but each with a different direction. A multiscale
analysis of the magnetic field shows that on the scale of a few times
the mean radial dimension of the molecular cloud, it is as if the
magnetic field were ``blind'' to the spatial distribution of the
filaments, while on smaller scales in the core region, multiwavelength
polarimetry shows a rotation of the magnetic field lines in these denser
phases. Finally, the Chandrasekhar and Fermi method is used to evaluate
the magnetic field strength, indicating that the core region is
approximately magnetically critical. A global interpretation suggests
that in the core region an original poloidal field could have been
twisted by a rotating elongated (core+envelope) structure. There is no
evidence for turbulence, and ambipolar diffusion does not seem to be
effective at the present time.