Evidence for H2 Formation Driven Dust Grain Alignment in IC 63

Type Journal Article
Names B.-G. Andersson, V. Piirola, J. De Buizer, D. P. Clemens, A. Uomoto, M. Charcos-Llorens, T. R. Geballe, A. Lazarian, T. Hoang, T. Vornanen
Publication The Astrophysical Journal
Volume 775
Pages 84
Journal Abbreviation The Astrophysical Journal
Date October 1, 2013
DOI 10.1088/0004-637X/775/2/84
ISSN 0004-637X
URL http://adsabs.org/2013ApJ.775.84A
Library Catalog labs.adsabs.harvard.edu
Abstract 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 H2 formation, by showing that the polarization of the light from stars behind the reflection nebula IC 63 appears to correlate with the intensity of H2 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 H2 formation and a probe of the dust characteristics, these results also provide one of the first direct confirmations of the grain-surface formation of H2. We compare our observations to ab initio modeling based on Radiative Torque Alignment (RAT) theory.
Tags DUST, ISM: individual objects: IC 63, ISM: magnetic fields, Polarization, extinction
UW-Madison Astronomy Home