DISCOVERY OF INTERSTELLAR ANIONS IN CEPHEUS AND AURIGA
- Astrochemistry Laboratory and The Goddard Center for Astrobiology, NASA Goddard Space Flight Center, Code 691, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)
- Cavendish Astrophysics Group and Kavli Institute for Cosmology, Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HE (United Kingdom)
We report the detection of microwave emission lines from the hydrocarbon anion C{sub 6}H{sup -} and its parent neutral C{sub 6}H in the star-forming region L1251A (in Cepheus), and the pre-stellar core L1512 (in Auriga). The carbon-chain-bearing species C{sub 4}H, HC{sub 3}N, HC{sub 5}N, HC{sub 7}N, and C{sub 3}S are also detected in large abundances. The observations of L1251A constitute the first detections of anions and long-chain polyynes and cyanopolyynes (with more than five carbon atoms) in the Cepheus Flare star-forming region, and the first detection of anions in the vicinity of a protostar outside of the Taurus molecular cloud complex, indicating a possible wider importance for anions in the chemistry of star formation. Rotational excitation temperatures have been derived from the HC{sub 3}N hyperfine structure lines and are found to be 6.2 K for L1251A and 8.7 K for L1512. The anion-to-neutral ratios are 3.6% and 4.1%, respectively, which are within the range of values previously observed in the interstellar medium, and suggest a relative uniformity in the processes governing anion abundances in different dense interstellar clouds. This research contributes toward the growing body of evidence that carbon chain anions are relatively abundant in interstellar clouds throughout the Galaxy, but especially in the regions of relatively high density and high depletion surrounding pre-stellar cores and young, embedded protostars.
- OSTI ID:
- 21560427
- Journal Information:
- Astrophysical Journal Letters, Vol. 730, Issue 2; Other Information: DOI: 10.1088/2041-8205/730/2/L18; ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
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