Discovery Of CH3CHCO In Taurus Molecular Cloud (TMC-1) With The QUIJOTE Line Survey

By Keith Cowing
Status Report
February 20, 2023
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Discovery Of CH3CHCO In Taurus Molecular Cloud (TMC-1) With The QUIJOTE Line Survey
Observed transitions with Ka = 0,1 of CH3CHCO in TMC-1. The abscissa corresponds to the rest frequency of the lines. Frequencies and intensities for the observed lines are given in Table A.1. The ordinate is the antenna temperature, corrected for atmospheric and telescope losses, in millikelvin. The quantum numbers of each transition are indicated in the corresponding panel. The red line shows the computed synthetic spectrum for this species for Trot=9 K and a column density of 1.5×1011 cm−2 . Blanked channels correspond to negative features produced in the folding of the frequency-switching data. Green labels indicate the transitions for which only one of the frequency-switching data points has been used (FS10 and FS8 correspond to a throw of 10 and 8 MHz, respectively). The dotted line in each panel indicates the 3σ value. — astro-ph.GA

We report the detection of methyl ketene towards TMC-1 with the QUIJOTE line survey. Nineteen rotational transitions with rotational quantum numbers ranging from J = 3 up to J = 5 and Ka =< 2 were identified in the frequency range 32.0-50.4 GHz, 11 of which arise above the 3{\sigma} level.

We derived a column density for CH3CHCO of N=1.5×10^11 cm-2 and a rotational temperature of 9 K. Hence, the abundance ratio between ketene and methyl ketene, CH2CO/CH3CHCO, is 93. This species is the second C3H4O isomer detected. The other, trans-propenal (CH2CHCHO), corresponds to the most stable isomer and has a column density of N=(2.2+-0.3)x10^11 cm-2, which results in an abundance ratio CH2CHCHO/CH3CHCO of 1.5.

The next non-detected isomer with the lowest energy is cis-propenal, which is therefore a good candidate for future discovery. We have carried out an in-depth study of the possible gas-phase chemical reactions involving methyl ketene to explain the abundance detected, achieving good agreement between chemical models and observations.

R. Fuentetaja, C .Bermúdez, C. Cabezas, M. Agúndez, B. Tercero, N. Marcelino, J. R. Pardo, L. Margulès, R. A. Motiyenko, J. -C. Guillemin, P. de Vicente, J. Cernicharo

Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2302.08825 [astro-ph.GA] (or arXiv:2302.08825v1 [astro-ph.GA] for this version)
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Submission history
From: Raúl Fuentetaja
[v1] Fri, 17 Feb 2023 11:47:33 UTC (145 KB)
Astrobiology, Astrochemistry

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