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          Institute: MPI für Radioastronomie     Collection: Publikationen des MPI für Radioastronomie     Display Documents

ID: 11209.0, MPI für Radioastronomie / Publikationen des MPI für Radioastronomie
Detection of a vibration-rotation emission line of hydrogen deuteride toward Orion Peak - 1 : excitation coupling of HD to H2
Authors:Ramsey Howat, S. K.; Timmermann, R.; Geballe, T. R.; Bertoldi, F.; Mountain, C. M.
Date of Publication (YYYY-MM-DD):2002-02-20
Title of Journal:Astrophysical Journal
Journal Abbrev.:Astrophys. J
Issue / Number:2
Start Page:905
End Page:909
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:The 2.46 mum upsilon = 1 - 0 R(5) line of deuterated molecular hydrogen (HD) has been detected in the Orion Peak 1 shock emission region, at a surface brightness of (8.5 +/- 2.1) x 10(-9)W m(-2)sr(-1) over a 6 arcsec(2) area. Comparison of the column density of HD (upsilon = 1, J = 6) with the column density of HD (upsilon = 0, J = 6) previously observed from the Infrared Space Observatory (ISO) and the H-2 level column densities toward the same region implies that the excitation of HD is similar to that of H-2 for these energy levels, despite much higher spontaneous transition rates for HD. We suggest that this rough equality is caused by the coupling of the HD levels to those of H-2, due to strong reactive collisions, HD + H <-> H-2 + D, in warm, partially dissociated gas. The deuterium abundance implied by the combined ISO and UKIRT measurements toward Orion Peak 1 is [D]/[H] = (5.1 +/- 1.9) x 10(-6).
Free Keywords:infrared : ISM; ISM : abundances; ISM : individual (Orion); ISM : lines and bands
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Radioastronomie
External Affiliations:Royal Observ, United Kingdom Astron Technol Ctr, Blackford; Hill, Edinburgh EH9 3HJ, Midlothian, Scotland; Royal Observ, United Kingdom Astron Technol Ctr, Edinburgh EH9 3HJ, Midlothian, Scotland; Univ Cologne, Inst Phys 1, D-50937 Cologne, Germany; Gemini Observ, Hilo, HI 96720 USA; Max Planck Inst Radioastron, D-53121 Bonn, Germany
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