Astrochemistry

The Rotation-tunneling Spectrum Of 3-hydroxypropenal And Confirmation Of Its Detection Toward IRAS 16293−2422 B

By Keith Cowing

Status Report

astro-ph.GA

May 3, 2024

Filed under 3-Hydroxypropenal, ALMA, astro-ph.GA, astrochemistry, biochemistry, Interstellar, IRAS 16293−2422 B, malonaldehyde, organic chemistry, Protostellar Interferometric Line Survey, Spectroscopy

The Rotation-tunneling Spectrum Of 3-hydroxypropenal And Confirmation Of Its Detection Toward IRAS 16293−2422 B — Undetected lines of 3-hydroxypropenal that are predicted above 3σ with the new spectroscopic data and the parameters previously constrained by Coutens et al. (2022) for an excitation temperature T_ex = 300 K. The PILS observations are in black. The model in red has been obtained with the best-fit parameters derived by Coutens et al. (2022) for T_ex = 300 K, i.e. with a column density N = 1.8 × 10¹⁵ cm⁻² . For comparison, the model obtained for T_ex = 125 K (N = 1.0 × 10¹⁵ cm⁻² ) is added in magenta. The cyan dotted line represents the 3 rms level per 0.33 km s⁻¹ (1/3 of the line width). — astro-ph.GA

3-Hydroxypropenal (HOCHCHCHO) is the lower energy tautomer of malonaldehyde which displays a complex rotation-tunneling spectrum.

It was detected tentatively toward the solar-type protostar IRAS 16293−2422 B with ALMA in the framework of the Protostellar Interferometric Line Survey (PILS). Several transitions, however, had large residuals, preventing not only their detection, but also the excitation temperature of the species from being determined unambiguously.

We want to extend the existing rotational line list of 3-hydroxypropenal to shed more light on the recent observational results and to facilitate additional radio astronomical searches for this molecule. We analyzed the rotation-tunneling spectrum of 3-hydroxypropenal in the frequency regions between 150 and 330 GHz and between 400 and 660 GHz. Transitions were searched for in the PILS observations of IRAS 16293−2422. Local thermodynamic equilibrium (LTE) models were carried out and compared to the observations to constrain the excitation temperature.

Additional transitions were searched for in other ALMA archival data of the same source to confirm the presence of 3-hydroxypropenal. More than 11500 transitions were assigned in the course of our investigation with quantum numbers 2≤J≤100, Ka≤59, and Kc≤97, resulting in a greatly improved set of spectroscopic parameters. The comparison between the LTE models and the observations yields an excitation temperature of 125 K with a column density N=1.0×10¹⁵ cm⁻² for this species.

We identified seven additional lines of 3-hydroxypropenal that show a good agreement with the model in the ALMA archive data. The calculated rotation-tunneling spectrum of 3-hydroxypropenal has sufficient accuracy for radio astronomical searches. The detection of 3-hydroxypropenal toward IRAS 16293−2422 B is now secure.

H. S. P. Müller, A. Coutens, J. K. Jørgensen, L. Margulès, R. A. Motiyenko, J.-C. Guillemin

Comments: 11 pages with figures, tables, and references. Abstract here slightly abbreviated. Accepted at Astron. Astrophys
Subjects: Astrophysics of Galaxies (astro-ph.GA); Solar and Stellar Astrophysics (astro-ph.SR); Chemical Physics (physics.chem-ph)
Cite as: arXiv:2405.01338 [astro-ph.GA] (or arXiv:2405.01338v1 [astro-ph.GA] for this version)
Submission history
From: Holger Müller
[v1] Thu, 2 May 2024 14:43:44 UTC (2,143 KB)
https://arxiv.org/abs/2405.01338
Astrobiology, astrochemistry,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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