Discovery of the Pure Polycyclic Aromatic Hydrocarbon Indene (c-C9H8) with GOTHAM Observations of TMC-1

Burkhardt, Andrew M.; Lee, Kelvin; Changala, P. Bryan; Shingledecker, Christopher N.; Cooke, Ilsa R.; Loomis, Ryan A.; Wei, Hongji; Charnley, Steven B.; Herbst, Eric; McCarthy, Michael; McGuire, Brett A.

doi:10.3847/2041-8213/abfd3a

Cited by 149 publications

(134 citation statements)

References 67 publications

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“…Among the QUIJOTE detections, we stress those of indene, the first double-cycle detected in space (Fig. 6 and 7 and Cernicharo et al 2021c; see also Burkhardt et al 2021), of cyclopentadiene (Cernicharo et al 2021d), and ortho-benzyne (Cernicharo et al 2021c). Detections reported by the GOTHAM and QUIJOTE teams include ethynyl and cyano derivatives of cyclopentadiene, benzene, and naphthalene (McCarthy et al 2021; see also Cernicharo et al 2021f).…”

Section: Complex Organic Molecules In the Dark Cloud Tmc-1mentioning

confidence: 74%

Organic Molecules in Insterstellar Space: Latest advances

Guèlin¹,

Cernicharo²

2022

Preprint

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Although first considered as too diluted for the formation of molecules in-situ and too harsh an environment for their survival, the interstellar medium has turned out to host a rich palette of molecular species: to date, 256 species, not counting isotopologues, have been identified. The last decade, and more particularly the last two years, have seen an explosion of new detections, including those of a number of complex organic species, which may be dubbed as prebiotic. Organic molecules have been discovered not just in interstellar clouds from the Solar neighbourhood, but also throughout the Milky-Way, as well as in nearby galaxies, or some of the most distant quasars.These discoveries were made possible by the completion of large sub-millimetre and radio facilities. Equipped with new generation receivers, those instruments have provided the orders of magnitude leap in sensitivity required to detect the vanishingly weak rotational lines that allowed the molecule identifications.Last two years, 30 prebiotic molecules have been detected in TMC-1, a dust-enshrouded gaseous cloud located at 400 light-years from the Sun in the Taurus constellation. Ten new molecular species, have been identified in the arm of a spiral galaxy 6 billion light-yr distant, and 12 molecular species observed in a quasar at 11 billion light-yr. We present the latest spectral observations of this outlying quasar and discuss the implications of those detections in these 3 archetypal sources. The basic ingredients involved in the Miller-Urey experiment and related experiments (H 2 , H 2 O, CH 4 , NH 3 , CO, H 2 S,...) appeared early after the formation of the first galaxies and are widespread throughout the Universe. The chemical composition of the gas in distant galaxies seems not much different from that in the nearby interstellar clouds. It presumably comprises, like for TMC-1, aromatic rings and complex organic molecules putative precursors of the RNA nucleobases, except the lines of such complex species are too weak to be detected that far.

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Section: Complex Organic Molecules In the Dark Cloud Tmc-1mentioning

confidence: 74%

Organic Molecules in Insterstellar Space: Latest advances

Guèlin¹,

Cernicharo²

2022

Preprint

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“…For the MCPs, no additional reactions or rates were added from the KIDA network beyond the related adaptations from other recent molecular detections (e.g. the expanded semi-saturated carbon-chain networks for HC 4 NC (Xue et al 2020), C 6 H 5 CN (Burkhardt et al 2021a), H 2 CCCHC 3 N (Shingledecker et al 2021), and indene (Burkhardt et al 2021b)).…”

Section: Chemical Modeling Of Methyl Chainsmentioning

confidence: 99%

“…In addition, the observed MP trend line can be reproduced well and is also analogous to what is observed for C n H. The estimated branching ratios and reaction rates still remain a major source of uncertainties in the models, which provide a strong motivation for further laboratory and theoretical studies. As discussed in Burkhardt et al (2021b), detailed study of increasing larger molecules (e.g. molecules with 7+ heavy atoms and/or aromatic rings) will likely require a rigorous study of the formation of semi-saturated carbon chains that have historically been performed piecewise.…”

Section: Chemical Modeling Of Methyl Chainsmentioning

confidence: 99%

CH3-Terminated Carbon Chains in the GOTHAM Survey of TMC-1: Evidence of Interstellar CH3C7N

Siebert,

Lee,

Remijan

et al. 2021

Preprint

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We report a systematic study of all known methyl carbon chains toward TMC-1 using the second data release of the GOTHAM survey, as well as a search for larger species. Using Markov-Chain Monte Carlo simulations and spectral line stacking of over 30 rotational transitions, we report statistically significant emission from methylcyanotriacetylene (CH 3 C 7 N) at a confidence level of 4.6σ, and use it to derive a column density of ∼10 11 cm −2 . We also searched for the related species, methyltetraacetylene (CH 3 C 8 H), and place upper limits on the column density of this molecule. By carrying out the above statistical analyses for all other previously detected methyl-terminated carbon chains that have emission lines in our survey, we assess the abundances, excitation conditions, and formation chemistry of methylpolyynes (CH 3 C 2n H) and methylcyanopolyynes (CH 3 C 2n -1 N) in TMC-1, and compare those with predictions from a chemical model. Based on our observed trends in column density and relative populations of the A and E nuclear spin isomers, we find that the methylpolyynes and methylcyanopolyynes families exhibit stark differences from one another, pointing to separate interstellar formation pathways, which is confirmed through gas-grain chemical modeling with nautilus.

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“…The on going line surveys of the Taurus Molecular Cloud 1 (TMC-1) at the Green Bank telescope (GOTHAM; McGuire et al 2020) and at the Yebes 40m telescope (QUIJOTE; Cernicharo et al 2021d), are demonstrating that complex hydrocarbons, including cyclic and polycyclic aromatic ones, are formed in situ in cold dense clouds. Examples of such molecules detected toward TMC-1 are propylene (CH 2 CHCH 3 ), vinyl and allenyl acetylene (CH 2 CHCCH and CH 2 CCHCCH), cyclopentadiene (c-C 5 H 6 ), indene (c-C 9 H 8 ), and benzyne (o-C 6 H 4 ) (Marcelino et al 2007;Cernicharo et al 2021a,b,c,d;Burkhardt et al 2021). Moreover, ethyl acetylene (CH 3 CH 2 CCH) and ethynyl benzene (c-C 6 H 5 CCH) have been tentatively detected (Cernicharo et al 2021a,e), and there is strong evidence for the presence of aromatic rings such as benzene and naphthalene from the detection of their CN derivatives (McGuire et al 2018(McGuire et al , 2021Cernicharo et al 2021e).…”

Section: Introductionmentioning

confidence: 99%

Detection of the propargyl radical at lambda 3 mm

Agundez,

Marcelino,

Cabezas

et al. 2021

Preprint

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We report the detection of the propargyl radical (CH 2 CCH) in the cold dark cloud TMC-1 in the λ 3 mm wavelength band. We recently discovered this species in space toward the same source at a wavelength of λ 8 mm. In those observations, various hyperfine components of the 2 0,2 -1 0,1 rotational transition, at 37.5 GHz, were detected using the Yebes 40m telescope. Here, we used the IRAM 30m telescope to detect ten hyperfine components of the 5 0,5 -4 0,4 rotational transition, lying at 93.6 GHz. The observed frequencies differ by 0.2 MHz with respect to the predictions from available laboratory data. This difference is significant for a radioastronomical search for CH 2 CCH in interstellar sources with narrow lines. We thus included the measured frequencies in a new spectroscopic analysis to provide accurate frequency predictions for the interstellar search for propargyl at mm wavelengths. Moreover, we recommend that future searches for CH 2 CCH in cold interstellar clouds are carried out at λ 3 mm, rather than at λ 8 mm. The 5 0,5 -4 0,4 transition is about five times more intense than the 2 0,2 -1 0,1 one in TMC-1, which implies that detecting the former requires about seven times less telescope time than detecting the latter. We constrain the rotational temperature of CH 2 CCH in TMC-1 to 9.9 ± 1.5 K, which indicates that the rotational levels of this species are thermalized at the gas kinetic temperature. The revised value of the column density of CH 2 CCH (including ortho and para species) is (1.0 ± 0.2) × 10 14 cm −2 , and thus the CH 2 CCH/CH 3 CCH abundance ratio is revised from slightly below one to nearly one. This study opens the door for future detections of CH 2 CCH in other cold interstellar clouds, making possible to further investigate the role of this very abundant hydrocarbon radical in the synthesis of large organic molecules such as aromatic rings.

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Discovery of the Pure Polycyclic Aromatic Hydrocarbon Indene (c-C9H8) with GOTHAM Observations of TMC-1

Cited by 149 publications

References 67 publications

Organic Molecules in Insterstellar Space: Latest advances

Organic Molecules in Insterstellar Space: Latest advances

CH3-Terminated Carbon Chains in the GOTHAM Survey of TMC-1: Evidence of Interstellar CH3C7N

Detection of the propargyl radical at lambda 3 mm

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