Magnetic Field Strengths and Grain Alignment Variations in the Local Bubble Wall

Wednesday, August 31, 2016 - 3:30pm PDT
Ilija Medan
St. Clara University
N232, room 103
Event Type: 

Optical and infrared continuum polarization is known to be due to irregular dust grains aligned with the local magnetic field.  This provides an important tool to probe the geometry and strength of those magnetic fields, particularly if the variations in the grain alignment efficiencies can be understood. In this study we combined archival photometric and spectroscopic data with the polarization survey of the North Galactic cap from Berdyugin et al. (2014), comparing it to the mapping of the Local Bubble by Lallement et al. (2003) to show that the alignment of the grains is directly related to the intensity of the illuminating field. The variations in grain alignment in the bubble wall can be seen to reflect the presence of all known OB associations within 200 pc of the Sun. We also probed the relative strength of the magnetic field in the wall of the local bubble using the Chandrasekhar-Fermi method and the results from Andersson & Potter (2006). We found evidence for a bimodal field strength distribution, where the higher strength might represent the compression of the wall by the outflow of the Local Bubble and the opposing effect by the surrounding OB associations.

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