Bibcode
Poidevin, Frederick
Bibliographical reference
Proquest Dissertations And Theses 2006. Section 0992, Part 0606 251 pages; [Ph.D. dissertation].Canada: Universite de Montreal (Canada); 2006. Publication Number: AAT NR24469. Source: DAI-B 68/03, Sep 2007
Advertised on:
12
2006
Citations
0
Refereed citations
0
Description
Together with other observational methods, visible and near infra-red
polarimetry can help to understand the morphology of magnetic fields in
the neighborhood of several star-forming regions. Inside molecular
clouds, this morphology can be deduced with the help of submm
polarimetry but rarely in the same regions. When both observational
methods are used for the same region, there is a gap in the spatial
scales to correctly compare the Galactic magnetic field with the
magnetic field probed inside the clouds.
This thesis proposes the necessary steps to make this type of
multi-scale analysis and to better understand the role that can be
played by magnetic fields in stellar formation regions. The GF 9 region
is the first region analysed with this method. Then, a study of the
morphology of the magnetic field located in filamentary molecular clouds
OMC-2 and OMC-3 is presented, followed by a multi-scale analysis of the
Orion A region, the molecular cloud complex in which these clouds are
embedded.
The results covering both regions can be summarized as follows. It is
statistically shown that the large scale morphology of the field is
poloidal in the GF 9 region, and probably toroidal in the Orion A
complex. On the smaller spatial scale of the envelopes of the clouds,
the magnetic fields appear to be aligned with the fields at their
periphery. On the spatial scale of cores, the poloidal magnetic field
located in the vicinity of GF 9 is apparently twisted and entrained by
the rotation of the core and ambipolar diffusion does not seem to be
effective at the present time. In Orion A, the morphology of the fields
can hardly be probed in active sites of stellar formation in OMC-2, and
is strongly constrained by the effects of gravity in OMC-1. There is no
evidence for turbulence in all the observed regions.
All in all, the multi-scale analyses suggest that independently of the
evolutionary state or of the range in mass of the star-forming regions,
the magnetic field morphology is significantly affected on spatial
scales similar to those of cores, in the same way that molecular cloud
properties remain self- similar down to the spatial scales similar to
those of cores.