This article has an erratum: [erratum]
Volume 486, Number 2, August I 2008
|Page(s)||493 - 496|
|Section||Interstellar and circumstellar matter|
|Published online||22 May 2008|
National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA, 22903-2475, USA e-mail: email@example.com
2 Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 Saint Martin d'Hères, France
3 Obs. de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
Accepted: 10 May 2008
Context. An unexpectedly complex polyatomic chemistry exists in diffuse clouds, allowing detection of species such as C2H, C3H2, H2CO, and NH3, which have relative abundances that are strikingly similar to those inferred toward the dark cloud TMC-1.
Aims. We probe the limits of complexity of diffuse cloud polyatomic chemistry.
Methods. We used the IRAM Plateau de Bure Interferometer to search for galactic absorption from low-lying J = 2-1 rotational transitions of A- and E-CH3OH near 96.740 GHz and used the VLA to search for the J = 8-7 transition of HC5N at 21.3 GHz.
Results. Neither CH3OH nor HC5N were detected at column densities well below those of all polyatomics known in diffuse clouds and somewhat below the levels expected from comparison with TMC-1. The HCN/HC5N ratio is at least 3–10 times higher in diffuse gas than toward TMC-1.
Key words: ISM: molecules / astrochemistry / ISM: clouds
© ESO, 2008
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