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| Paper: |
Observational Evidence for Radiative Interstellar
Grain Alignment |
| Volume: |
449, Astronomical Polarimetry 2008: Science from Small to Large Telescopes |
| Page: |
134 |
| Authors: |
Andersson, B.; Potter, S. B.; Andersson, B.; Potter, S. |
| Abstract: |
The alignment mechanisms of interstellar dust grains is a long standing astrophysical problem. Interstellar polarization was first discovered in 1949 and soon thereafter attributed to dichroic extinction caused by asymmetric dust grains aligned with the magnetic field. For a long time the alignment mechanism was thought to involve paramagnetic relaxation in rapidly spinning dust grains. Modern theory indicates that the classical alignment mechanisms are likely not efficient, but rather favor alignment through direct radiative torques. We have used multi-band polarimetry towards stars probing six nearby clouds to show that the wavelength of maximum polarization is linearly correlated with the visual extinction (Andersson & Potter 2007; AP07; where further details can be found). We find a universal relation with a common positive slope between the clouds and a DC offset correlated with the average of the total-to-selective extinction < RV > . These results provide strong observational support for radiatively driven grain alignment. Recent observations of an additional set of ≈60 sightlines in the Taurus cloud confirm and strengthen these results. |
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