ON THE UBIQUITY OF MOLECULAR ANIONS IN THE DENSE INTERSTELLAR MEDIUM
Journal article, 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-.

line

stars: formation

tmc-1

dark clouds

star-formation

astrochemistry

cores

ISM: clouds

observations

carbon-chain molecules

ISM: molecules

chemistry

c6h

millimeter

negative-ions

ISM: abundances

Author

M. A. Cordiner

J. V. Buckle

Eva Wirström

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

Henrik Olofsson

Chalmers, Earth and Space Sciences, Onsala Space Observatory

S. B. Charnley

V. P. Nada

Astrophysical Journal

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

Vol. 770 1 48

Subject Categories

Astronomy, Astrophysics and Cosmology

DOI

10.1088/0004-637x/770/1/48

More information

Created

10/7/2017