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[15.07] Interstellar H₃⁺ Line Absorption Toward LkH\alpha 101

S. D. Brittain, T. W. Rettig (University of Notre Dame)

We present a detection of three lines of the H₃⁺ ion in the near-infrared spectrum of the Herbig Be star, LkH\alpha 101. H₃⁺ is the principal initiator of gas phase chemistry in interstellar clouds and can be used to constrain the ionization rate or the path length through interstellar material along the line of sight. Essentially all of the observed H₃⁺ column of 2.2±0.3 x 10¹⁴ cm^-2 toward LkH\alpha 101 originates in the same dense, dark cloud; less than 1 magnitude of the ~11 total magnitudes of visual extinction is attributable to diffuse material. The non-detection of fluorescent H₂ emission at the cloud surface implies that the obscuring dark cloud is located at least 20pc from LkH\alpha 101 and is therefore decoupled from its evolution. The confirmation of significant H₃⁺ in dense material addresses earlier concerns that H₃⁺ may originate in diffuse material surrounding dense clouds.

This work was supported by the National Science Foundation.

The author(s) of this abstract have provided an email address for comments about the abstract: sbrittai@nd.edu

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Bulletin of the American Astronomical Society, 36 #2
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