Volume 577, May 2015
|Number of page(s)||6|
|Published online||20 May 2015|
Instituto de Ciencia de Materiales de Madrid,
CSIC, C/ Sor Juana Inés de la Cruz
2 Institut de Radioastronomie Millimétrique, 300 rue de la Piscine, 38406 St.-Martin d’Hères, France
Received: 15 April 2015
Accepted: 22 April 2015
We conducted radioastronomical observations of 9 dark clouds with the IRAM 30 m telescope. We present the first identification in space of the ketenyl radical (HCCO) toward the starless core Lupus-1A and the molecular cloud L483 and the detection of the related molecules ketene (H2CCO) and acetaldehyde (CH3CHO) in these two sources and 3 additional dark clouds. We also report the detection of the formyl radical (HCO) in the 9 targeted sources and of propylene (CH2CHCH3) in 4 of the observed sources, which significantly extends the number of dark clouds where these molecules are known to be present. We have derived a beam-averaged column density of HCCO of ~5 × 1011 cm-2 in both Lupus-1A and L483, which means that the ketenyl radical is just ~10 times less abundant than ketene in these sources. The non-negligible abundance of HCCO found implies that there must be a powerful formation mechanism able to counterbalance the efficient destruction of this radical through reactions with neutral atoms. The column densities derived for HCO, (0.5–2.7) ×1012 cm-2, and CH2CHCH3, (1.9–4–2) ×1013 cm-2, are remarkably uniform across the sources where these species are detected, confirming their ubiquity in dark clouds. Gas phase chemical models of cold dark clouds can reproduce the observed abundances of HCO, but cannot explain the presence of HCCO in Lupus-1A and L483 and the high abundances derived for propylene. The chemistry of cold dark clouds needs to be revised in light of these new observational results.
Key words: astrochemistry / line: identification / ISM: clouds / ISM: molecules / radio lines: ISM
Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).
Tables 3–6 are available in electronic form at http://www.aanda.org
© ESO, 2015
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