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The TMRT K band observations towards 26 infrared dark clouds: NH3, CCS, and HC3N

Xie, Jinjin, Fuller, Gary A., Li, Di, Chen, Longfei, Ren, Zhiyuan, Wu, Jingwen, Duan, Yan, Wang, Junzhi, Li, Juan, Peretto, Nicolas ORCID:, Liu, Tie and Shen, Zhiqiang 2021. The TMRT K band observations towards 26 infrared dark clouds: NH3, CCS, and HC3N. SCIENCE CHINA Physics, Mechanics and Astronomy 64 (7) , 279511. 10.1007/s11433-021-1695-0

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We present one of the first Shanghai Tian Ma Radio Telescope (TMRT) K Band observations towards a sample of 26 infrared dark clouds (IRDCs). We observed the (1,1), (2,2), (3,3), and (4,4) transitions of NH3 together with CCS (21–>10) and HC3N J = 2–1, simultaneously. The survey dramatically increases the existing CCS-detected IRDC sample from 8 to 23, enabling a better statistical study of the ratios of carbon-chain molecules (CCM) to N-bearing molecules in IRDCs. With the newly developed hyperfine group ratio (HFGR) method of fitting NH3 inversion lines, we found the gas temperature to be between 10 and 18 K. The column density ratios of CCS to NH3 for most of the IRDCs are less than 10−2, distinguishing IRDCs from low-mass star-forming regions. We carried out chemical evolution simulations based on a three-phase chemical model NAUTILUS. Our measurements of the column density ratios between CCM and NH3 are consistent with chemical evolutionary ages of ≲105 yr in the models. Comparisons of the data and chemical models suggest that CCS, HC3N, and NH3 are sensitive to the chemical evolutionary stages of the sources.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Publisher: Springer Verlag
ISSN: 1674-7348
Date of First Compliant Deposit: 15 June 2021
Date of Acceptance: 23 March 2021
Last Modified: 09 Nov 2022 11:07

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