2013ApJ...770...48C -
Astrophys. J., 770, 48 (2013/June-2)
On the ubiquity of molecular anions in the dense interstellar medium.
CORDINER M.A., BUCKLE J.V., WIRSTROM E.S., OLOFSSON A.O.H. and CHARNLEY S.B.
Abstract (from CDS):
Result. are presented from a survey for molecular anions in seven nearby Galactic star-forming cores and molecular clouds. The hydrocarbon anion C6H– is detected in all seven target sources, including four sources where no anions have been previously detected: L1172, L1389, L1495B, and TMC-1C. The C6H–/C6 H column density ratio is ≳ 1.0% in every source, with a mean value of 3.0% (and standard deviation 0.92%). Combined with previous detections, our results show that anions are ubiquitous in dense clouds wherever C6 H is present. The C6H–/C6H ratio is found to show a positive correlation with molecular hydrogen number density, and with the apparent age of the cloud. We also report the first detection of C4H– in TMC-1 (at 4.8σ confidence), and derive an anion-to-neutral ratio C4H–/C4 H =(1.2 ± 0.4)x10–5(= 0.0012%±0.0004%). Such a low value compared with C6H– highlights the need for a revised radiative electron attachment rate for C4H. Chemical model calculations show that the observed C4H– could be produced as a result of reactions of oxygen atoms with C5H– and C6H–.
Abstract Copyright:
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Journal keyword(s):
astrochemistry - ISM: abundances - ISM: clouds - ISM: molecules - stars: formation
Simbad objects:
25
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