Detection of Interstellar HC5O in TMC-1 with the Green Bank Telescope

We report the detection of the carbon-chain radical HC5O for the first time in the interstellar medium toward the dark cloud TMC-1 using the 100 m Green Bank Telescope.

We observe four hyperfine components of this radical in the J=17/2→15/2 rotational transition that originates from the 2Π1/2 fine structure level of its ground state, and calculate an abundance of n/nH2 = 1.7×10−10, assuming an excitation temperature of Tex=7~K. No indication of HC3O, HC4O, HC6O, is found in these or archival observations of the source, while we report tentative evidence for HC7O. We compare calculated upper limits, and the abundance of HC5O to predictions based on (1) the abundance trend of the analogous HCnN family in TMC-1 and (2) a gas-grain chemical model.

We find that the gas-grain chemical model well reproduces the observed abundance of HC5O, as well as the upper limits of HC3O, HC6O, and HC7O, but HC4O is over produced. The prospects for astronomical detection of both shorter and longer HCnO chains are discussed.

Brett A. McGuire, Andrew M. Burkhardt, Christopher N. Shingledecker, Sergei V. Kalenskii, Eric Herbst, Anthony J. Remijan, Michael C. McCarthy
(Submitted on 29 Jun 2017)

Comments: Accepted in The Astrophysical Journal Letters
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:1706.09766 [astro-ph.GA] (or arXiv:1706.09766v1 [astro-ph.GA] for this version)
Submission history
From: Brett McGuire
[v1] Thu, 29 Jun 2017 14:03:57 GMT (351kb,D)

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