Back to Volume
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.
Back to Volume