Detection of HC7O, non-detection of HC11N, and a Search For New Organic Molecules

The 100 m Robert C. Byrd Green Bank Telescope K-band (KFPA) receiver was used to perform a high-sensitivity search for rotational emission lines from complex organic molecules in the cold interstellar medium towards TMC-1 (cyanopolyyne peak)

The search focused on the identification of new carbon-chain-bearing species as well as molecules of possible prebiotic relevance.

We report a detection of the carbon-chain oxide species HC7O and derive a column density of (7.8±0.9)×1011~cm−2. This species is theorized to form as a result of associative electron detachment reactions between oxygen atoms and C7H−, and/or reaction of C6H2+ with CO (followed by dissociative electron recombination). Upper limits are given for the related HC6O, C6O and C7O molecules. In addition, we obtained the first detections of emission from individual 13C isotopologues of HC7N, and derive abundance ratios HC7N/HCCC13CCCCN = 110±16 and HC7N/HCCCC13CCCN = 96±11, indicative of significant 13C depletion in this species relative to the local interstellar elemental 12C/13C ratio of 60-70. The observed spectral region covered two transitions of HC11N, but emission from this species was not detected, and the corresponding column density upper limit is 7.4×1010 cm−2 (at 95% confidence). This is significantly lower than the value of 2.8×1011 cm−2 previously claimed by Bell et al. (1997) and confirms the recent non-detection of HC11N in TMC-1 by Loomis et al. (2016). Upper limits were also obtained for the column densities of malononitrile and the nitrogen heterocycles quinoline, isoquinoline and pyrimidine.

Deep K-band observations of TMC-1 with the Green Bank Telescope: Detection of HC7O, non-detection of HC11N, and a search for new organic molecules

M. A. Cordiner, S. B. Charnley, Z. Kisiel, B. A. McGuire, Y.-J. Kuan
(Submitted on 27 Oct 2017)

Comments: Accepted for publication in ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:1710.10178 [astro-ph.GA] (or arXiv:1710.10178v1 [astro-ph.GA] for this version)
Submission history
From: Martin Cordiner PhD
[v1] Fri, 27 Oct 2017 14:44:54 GMT (88kb,D)

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