ALMA Observations of CH3COCH3 and the Related Species CH3CHO, CH3OH, and C2H5CN in Line-rich Molecular Cores
Context. Acetone (CH3COCH3) is a carbonyl-bearing complex organic molecule, yet interstellar observations of acetone remain limited. Studying the formation and distribution of CH3COCH3. in the interstellar medium can provide valuable insights into prebiotic chemistry and the evolution of interstellar molecules.
Aims. We explore the spatial distribution of CH3COCH3 and its correlation with the O-bearing molecules acetaldehyde (CH3CHO) and methanol (CH3OH), as well as the N-bearing molecule ethyl cyanide (C2H5CN), in massive protostellar clumps.
Methods. We observed 11 massive protostellar clumps using ALMA at 345 GHz, with an angular resolution of 0.7”-1.0”. Spectral line transitions were identified using the eXtended CASA Line Analysis Software Suite. We constructed integrated intensity maps of CH3COCH3, CH3CHO, CH3OH, and C2H5CN and derived their rotation temperatures, column densities, and abundances under the assumption of local thermodynamic equilibrium.
Continuum emission in gray scale at 870 µm overlaid with the integrated intensities of CH3COCH3, CH3CHO, CH3OH, and C2H5CN in nine high-mass star-forming regions. Colored contours represent the integrated intensities of each molecule. Contour levels are stepped by 10% of the peak values, with the outermost levels as follows: 4% for I14498, 6% for I15520, 10% for I15596, 1.3% for I16060, 1.3% for I16071, 5% for I16076, 1% for I16272, 0.8% for I16351, and 1.8% for I17220. Line-rich cores are named according to Li et al. (2024). The cross symbols mark the peak positions of the continuum emissions. The synthesized beam sizes are shown in the lower left, and scale bars are in the lower right. — astro-ph.GA
Results. CH3COCH3 is detected in 16 line-rich cores from 9 massive protostellar clumps: 12 high-mass cores, 3 intermediate-mass cores, and 1 low-mass core. CH3CHO and CH3OH are also detected in all 16 cores, while C2H5CN is detected in 15. The integrated intensity maps reveal similar spatial distributions for CH3COCH3, CH3CHO, CH3OH, and C2H5CN. The line emission peaks of all four molecules coincide with the continuum emission peaks in regions without ultracompact HII regions. Significant correlations are observed in the abundances of these molecules, which also exhibit similar average temperatures.
Conclusions. Our observational results, supported by chemical models, suggest that CH3COCH3, CH3CHO, and CH3OH originate from the same gas. The observed temperatures and abundances of CH3COCH3 are consistent with model predictions involving grain surface chemistry.
Spectra of IRAS 16272-4837 C3 in the frequency range 342.4−346.1 GHz. The observed spectra are shown as gray curves, and the XCLASS-modeled spectra as colored curves. Spectra of other sources are presented in Fig. B.1. — astro-ph.GA
Chuanshou Li, Sheng-Li Qin, Tie Liu, Xunchuan Liu, Xiaohu Li, Li Chen, Hong-Li Liu, Fengwei Xu, Meizhu Liu, Mengyao Tang, Hongqiong Shi, Tianwei Zhang, Yuefang Wu
Comments: 27 pages, 5 figures
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2503.07052 [astro-ph.GA] (or arXiv:2503.07052v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2503.07052
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Submission history
From: Chuanshou Li
[v1] Mon, 10 Mar 2025 08:39:10 UTC (1,545 KB)
https://arxiv.org/abs/2503.07052
Astrobiology, Astrochemistry,
