A Multitransition Methanol Survey toward a Large Sample of High-mass Star-forming Regions

Abstract We carried out a spectral line survey of CH 3 OH toward a large sample of 175 high-mass star-forming regions in the 3 mm, 2 mm, and 1.3 mm bands with the Institut de Radioastronomie Millimétrique (IRAM) 30 m telescope. Out of our 175 targets, 148 sources were detected with one or more CH 3...

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Bibliographic Details
Published in:The Astrophysical journal. Supplement series 2023-06, Vol.266 (2), p.29
Main Authors: Zhao, J. Y., Zhang, J. S., Wang, Y. X., Qiu, J. J., Yan, Y. T., Yu, H. Z., Chen, J. L., Zou, Y. P.
Format: Article
Language:English
Subjects:
Astrochemistry
Density ratio
Emission analysis
Emission lines
Interstellar molecules
Line spectra
Low temperature
Low temperature environments
Masers
Massive stars
Molecule formation
Rotational temperatures
Star formation
Target detection
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Summary:Abstract We carried out a spectral line survey of CH 3 OH toward a large sample of 175 high-mass star-forming regions in the 3 mm, 2 mm, and 1.3 mm bands with the Institut de Radioastronomie Millimétrique (IRAM) 30 m telescope. Out of our 175 targets, 148 sources were detected with one or more CH 3 OH transition lines. Nineteen CH 3 OH transition lines, including 13 thermal lines and 6 maser lines, were detected. The 8 0 → 7 1 A + (∼95.169 GHz) CH 3 OH maser line, one of the strongest class I CH 3 OH maser lines, was detected in 52 sources. Forty-two of them are previously reported masers and the other 10 are new detections. Through analyzing the rotational diagram of the detected CH 3 OH emission lines (nonmasing lines), we obtained the rotational temperature and the column density for 111 sources. Our results show that E -type CH 3 OH tends to have lower column density than A -type CH 3 OH. The column density ratio of E / A was derived in 55 sources with the majority having a ratio less than 1.0 (about 70%), with a peak ratio of ∼0.6. This is consistent with theoretical predictions, i.e., overabundance of A -type CH 3 OH at low temperature leading to a low E / A ratio. Furthermore, we found that CH 3 OH abundance decreases beyond T dust ∼ 30 K, which is supported by modeling results. All these support the fact that CH 3 OH is easily formed at low-temperature environments, via successive hydrogenation of CO on cold dust surfaces.
ISSN:0067-0049
1538-4365
DOI:10.3847/1538-4365/acc323