AAS Meeting #193 - Austin, Texas, January 1999
Session 65. Interstellar Dust and Gas
Display, Friday, January 8, 1999, 9:20am-6:30pm, Exhibit Hall 1

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[65.06] Observation of H3+ in Dense and Diffuse Clouds

B. J. McCall (U. Chicago), T. R. Geballe (Gemini), K. H. Hinkle (NOAO), T. Oka (U. Chicago)

The molecular ion H3+, which has long been considered the cornerstone of gas-phase chemistry in the interstellar medium, has now been detected in both dense and diffuse clouds.

The \nu2 vibrational band of H3+ near 3.67 \mum has been detected using the facility spectrometer CGS4 at the United Kingdom Infrared Telescope and the Phoenix high-resolution spectrometer at Kitt Peak National Observatory.

H3+ column densities of a few x 1014 cm-2 have been observed along the lines of sight to several embedded young stellar objects such as AFGL 2136. Simple chemical models of H3+ chemistry predict number densities of about 10-4 cm-3, independent of total number density. Using this calculation, the observations yield estimates of effective path length and total number densities toward these sources.

An unexpectedly large column density of H3+ (3.8 x 1014 cm-2) has also been detected towards the visible star Cygnus OB2 No. 12. Current models of diffuse cloud chemistry predict H3+ number densities two to three orders of magnitude lower than in diffuse clouds, implying much longer path lengths. Recent observations of other diffuse cloud sources will also be discussed.

H3+ has also been detected with column density greater than 1015 cm-2 towards the two galactic center sources IRS 3 and GCS 3-2. These observations are interpreted as arising from a combination of both dense and diffuse material.

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

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