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Title: CH{sup +} and SH{sup +} in the diffuse interstellar medium: Tracers of turbulent dissipation

Absorption spectroscopy performed with Herschel/HIFI against the dust continuum emission of bright galactic star-forming regions has allowed the detection of the ground-state transitions of several hydride cations, CH{sup +}, OH{sup +}, H{sub 2}O{sup +}, and SH{sup +} in the intervening diffuse medium. These hydrides, that need H{sub 2} to form but are also destroyed by H{sub 2}, appear to be most sensitive tracers of a poorly known component of the interstellar medium (ISM): molecular gas weakly shielded from UV radiation. Among them, because their formation routes are so highly endoenergic, the CH{sup +} and SH{sup +} cations are proposed to be specific tracers of turbulent dissipation occurring in diffuse gas. Their elusive origin in the diffuse ISM is therefore much more than a chemical riddle: it is rooted in the physics of the diffuse ISM, its turbulent dissipation rate and connects with the far broader issue of galaxy evolution. The Herschel/HIFI observations of CH{sup +} and SH{sup +} are compared with the predictions of chemical models that include the non-equilibrium effects of turbulent dissipation.
Authors:
; ;  [1] ;  [2]
  1. Observatoire de Paris and Ecole Normale Supérieure, Paris (France)
  2. Centro de Astrobiologia, CSIC-INTA, Madrid (Spain)
Publication Date:
OSTI Identifier:
22390905
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 1642; Journal Issue: 1; Conference: ICCMSE-2010: International Conference of Computational Methods in Sciences and Engineering 2010, Kos (Greece), 3-8 Oct 2010; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ABSORPTION SPECTROSCOPY; CATIONS; COMPARATIVE EVALUATIONS; DETECTION; EQUILIBRIUM; GALAXIES; GROUND STATES; HYDRIDES; HYDROGEN; INTERSTELLAR SPACE; MOLECULAR IONS; STAR EVOLUTION; STARS; ULTRAVIOLET RADIATION; WATER