Table of Contents
Title Page
H3+ in Interstellar Space
Detection Scheme
UKIRT & CGS4
Kitt Peak & Phoenix
H3+ Transitions Used
First Detection: Dense Cloud
Dense Cloud Environment
H3+ Chemistry
Dense Cloud Chemistry
H3+ in Diffuse Clouds!!!
Diffuse Cloud Environment
Diffuse Cloud Chemistry
Results for Cygnus OB2#12
A Long Path Length!
Conclusions
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Author: Benjamin J. McCall
Email: bjmccall@astro.berkeley.edu
Home Page: http://astro.berkeley.edu/~bjmccall
Other information:
Presented at the 53rd Ohio State University International Symposium on Molecular Spectroscopy, 1998, talk RD03. [15 minutes]
Abstract: H3+, the
cornerstone molecule of interstellar chemistry, was first detected in
interstellar space in 1996 (b) in the dense molecular clouds GL2136 and
W33A. We have now extended this ion's diagnostic powers to the diffuse
interstellar medium with the detection of H3+ along
the line of sight to the visible star Cygnus OB2 No. 12 (c). Three
rovibrational transitions in the 3.7 um region were observed using the
CGS4 infrared spectrometer at the United Kingdom Infrared Telescope and
the high resolution Phoenix spectrometer at the Kitt Peak National
Observatory.
We have developed a simple chemical model of interstellar chemistry which
describes the abundance of H3+ in both diffuse and
dense clouds. The application of this model to Cygnus OB2 No. 12 shows
that this line of sight has H3+ number density
[H3+]~4x10^-7 cm^-3, effective path length
L~300 pc, and hydrogen number density [H]+2[H2]~20 cm^-3. The
H3+ absorptions also provide an estimate of the
effective kinetic temperature of the medium T ~ 27 K.
(b) T. R. Geballe and T. Oka, Nature 384, 334 (1996).
(c) B. J. McCall, T. R. Geballe, K. H. Hinkle, and T. Oka, Science,
279, 1910 (1998)
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