ALMA Detection of Vibrationally Excited ($v{}_{\mathrm{t}}=1,2$) Acetic Acid toward NGC 6334I

Abstract

Vibrationally excited states of detected interstellar molecules have been shown to account for a large portion of unidentified spectral lines in observed interstellar spectra toward chemically rich sources. Here, we present the first interstellar detection of the first and second vibrationally excited torsional states of acetic acid ($v_{\mathrm{t}}=1,2$) toward the high-mass star-forming region NGC 6334I. The observations presented were taken with the Atacama Large Millimeter/submillimeter Array in bands 4, 6, and 7 covering a frequency range of 130 - 352 GHz. By comparing a single excitation temperature model to the observations, the best-fit excitation temperature and column density are obtained to be 142(25) K and $1.12(7)\times 10^{17}\mathrm{c}{\mathrm{m}}^{-2}$ respectively. Based on the intensity maps of the vibrationally excited CH${}_3$COOH transitions, we found that the CH${}_3$COOH emissions are compact and concentrated toward the MM1 and MM2 regions with a source size smaller than 2 arcsec. After locating the emission from different CH${}_3$COOH transitions, which cover a large range of excitation energies, we are able to explain the variation of the CH${}_3$COOH emission peak within the MM2 core by invoking continuum absorption or outflows.

15 pages, 5 figures

References in corpus (11)

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• {Millimeter Multiplicity in NGC 6334 I and I(N)
• ALMA Detection of Interstellar Methoxymethanol (CH${}_3$OCH${}_2$OH)
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• Antifreeze in the hot core of Orion - First detection of ethylene glycol in Orion-KL
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• Submillimeter spectroscopy of southern hot cores: NGC6334(I) and G327.3-0.6
• ATCA 3mm observations of NGC6334I and I(N): dense cores, outflows and an UCHII region
• ALMA Observations of the Spatial Distribution of three C${}_2$H${}_4$O${}_2$ Isomers towards Sgr B2(N)
• Laboratory spectroscopic study and astronomical detection of vibrationally excited n-propyl cyanide
• ALMA imaging study of methyl formate (HCOOCH${}_3$) in the torsionally excited states towards Orion KL

Cited by in corpus (4)

• The family of amide molecules toward NGC 6334I
• The Extraordinary Outburst in the Massive Protostellar System NGC6334I-MM1: Strong Increase in Mid-Infrared Continuum Emission
• The Role of Radiolysis in the Modelling of C${}_2$H${}_4$O${}_2$ Isomers and Dimethyl Ether in Cold Dark Clouds
• Expanding the submillimeter wave spectroscopy and astronomical search for thioacetamide (CH3CSNH2) in the ISM