AAS 204th Meeting, June 2004
Session 15 Diffuse Media Galactic and Intergalactic
Oral, Monday, May 31, 2004, 10:00-11:30am, 601

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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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