On the ubiquity of molecular anions in the dense interstellar medium
Artikel i vetenskaplig tidskrift, 2013

Results 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-/C6H column density ratio is greater than or similar to 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 C6H 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 4.8 sigma confidence), and derive an anion-to-neutral ratio C4H-/C4H = (1.2 +/- 0.4) x 10(-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-.

ISM: clouds

ISM: molecules


stars: formation

ISM: abundances


M. A. Cordiner

NASA Goddard Space Flight Center

Catholic University of America

J. V. Buckle

University of Cambridge

Eva Wirström

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

NASA Goddard Space Flight Center

Henrik Olofsson

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

S. B. Charnley

NASA Goddard Space Flight Center

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 770 1 48


Astronomi, astrofysik och kosmologi



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