Journal
ASTROPHYSICAL JOURNAL
Volume 775, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/775/2/84
Keywords
dust, extinction; ISM: individual objects (IC 63); ISM: magnetic fields; polarization
Categories
Funding
- NASA
- NSF
- W.M. Keck Foundation
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- NSF [AST-1109469, AST 06-07500, 09-07790]
- Gemini Observatory
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [0907790, 1109295] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Physics [0821899] Funding Source: National Science Foundation
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In the interstellar medium (ISM), molecular hydrogen is expected to form almost exclusively on the surfaces of dust grains. Due to that molecule's large formation energy (-4.5 eV), several dynamical effects are likely associated with the process, including the alignment of asymmetric dust grains with the ambient magnetic field. Such aligned dust grains are, in turn, believed to cause the broadband optical/infrared polarization observed in the ISM. Here, we present the first observational evidence for grain alignment driven by H-2 formation, by showing that the polarization of the light from stars behind the reflection nebula IC 63 appears to correlate with the intensity of H-2 fluorescence. While our results strongly suggest a role for Purcell rockets in grain alignment, additional observations are needed to conclusively confirm their role. By showing a direct connection between H-2 formation and a probe of the dust characteristics, these results also provide one of the first direct confirmations of the grain-surface formation of H-2. We compare our observations to ab initio modeling based on Radiative Torque Alignment (RAT) theory.
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