Detection of Interstellar HC${}_5$O in TMC-1 with the Green Bank Telescope

Abstract

We report the detection of the carbon-chain radical HC${}_5$O 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 $J=17/2\to 15/2$ rotational transition that originates from the ${}^2{\Pi }_{1/2}$ fine structure level of its ground state, and calculate an abundance of $n/n_{H_2}$ = $1.7\times 10^{-10}$, assuming an excitation temperature of $T_{ex}=7$~K. No indication of HC${}_3$O, HC${}_4$O, HC${}_6$O, is found in these or archival observations of the source, while we report tentative evidence for HC${}_7$O. We compare calculated upper limits, and the abundance of HC${}_5$O to predictions based on (1) the abundance trend of the analogous HC${}_n$N 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 HC${}_5$O, as well as the upper limits of HC${}_3$O, HC${}_6$O, and HC${}_7$O, but HC${}_4$O is over produced. The prospects for astronomical detection of both shorter and longer HC${}_n$O chains are discussed.

Accepted in The Astrophysical Journal Letters

References in corpus (5)

• The 2014 KIDA network for interstellar chemistry
• A New Reference Chemical Composition for TMC-1
• Herschel observations of EXtraordinary Sources: Analysis of the full Herschel/HIFI molecular line survey of Sagittarius B2(N)
• Investigating the Minimum Energy Principle in Searches for New Molecular Species - the Case of H${}_2$C${}_3$O Isomers
• Chemistry of TMC-1 with multiply deuterated species and spin chemistry of H2, H2+, H3+ and their isotopologues

Cited by in corpus (16)

• 2021 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules
• Discovery of the Pure Polycyclic Aromatic Hydrocarbon Indene ($c$-C${}_9$H${}_8$) with GOTHAM Observations of TMC-1
• Discovery of HC3O+ in space: The chemistry of O-bearing species in TMC-1
• Tentative detection of HC5NH+ in TMC-1
• Detection of Interstellar HC${}_4$NC and an Investigation of Isocyanopolyyne Chemistry under TMC-1 Conditions
• Carbon-Chain Chemistry in the Interstellar Medium
• The Case of H${}_2$C${}_3$O Isomers, Revisited: Solving the Mystery of the Missing Propadienone
• Discovery of the acetyl cation, CH3CO+, in space and in the laboratory
• 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
• Detection of HC${}_5$N and HC${}_7$N Isotopologues in TMC-1 with the Green Bank Telescope
• Discovery of HCCCO and C5O in TMC-1 with the QUIJOTE line survey
• Machine Learning of Interstellar Chemical Inventories
• Discovery of CH3CHCO in TMC-1 with the QUIJOTE line survey
• Carbon-Chain Molecules in Molecular Outflows and Lupus I Region--New Producing Region and New Forming Mechanism
• Millimetre and submillimetre spectroscopy of isobutene and its detection in the molecular cloud G+0.693
• Chemical variations across the TMC-1 boundary: molecular tracers from translucent phase to dense phase