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| Paper: |
The Magnetic Structure of the Pipe Nebula as Revealed by Optical Polarimetry |
| Volume: |
449, Astronomical Polarimetry 2008: Science from Small to Large Telescopes |
| Page: |
152 |
| Authors: |
Alves, F.; Franco, G.; Girart, J. M. |
| Abstract: |
Magnetic fields are proposed to play an important role in the formation
and support of self-gravitating clouds. We attempt to understand more
precisely how the Pipe nebula is affected by the magnetic field. We use
R-band linear polarimetry collected for about 12 000 stars with lines of
sight toward the Pipe nebula to investigate the properties of the
polarization across this dark cloud complex. Mean polarization vectors
show that the magnetic field is locally perpendicular to the large
filamentary structure of the Pipe nebula (the ‘stem'), indicating that
the global collapse may have been driven by ambipolar diffusion. The
northwestern end of the nebula (B59 region) is found to have a low
degree of polarization and high dispersion of position angles, while at
the other extreme of the cloud (the ‘bowl') we found mean degrees of
polarization as high as ≈ 15% and a low dispersion in
polarization position angles. The plane of sky magnetic field strength
was estimated to vary from about 17 μG in the B59 region to about 65
μG in the bowl. We propose that three distinct regions exist, which
may be related to different evolutionary stages of the cloud. |
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