Calculating the Excitation Temperature for H_2CO Absorption Lines in Molecular Clouds  

作　　者：Jia Bu Jarken Esimbek Jianjun Zhou Toktarkhan Komesh Xindi Tang Dalei Li Yuxin He Kadirya Tursun Dongdong Zhou Ernar Imanaly Serikbek Sailanbek 

机构地区：[1]Xinjiang Astronomical Observatory,Chinese Academy of Sciences,Urumqi 830011,China [2]University of Chinese Academy of Sciences,Beijing 100080,China [3]Key Laboratory of Radio Astronomy,Chinese Academy of Sciences,Urumqi 830011,China [4]Xinjiang Key Laboratory of Radio Astrophysics,Urumqi 830011,China [5]Energetic Cosmos Laboratory,Nazarbayev University,Astana 010000,Kazakhstan [6]Institute of Experimental and Theoretical Physics,Al-Farabi Kazakh National University,Almaty 050040,Kazakhstan

出　　处：《Research in Astronomy and Astrophysics》2024年第7期268-271,共4页天文和天体物理学研究（英文版）

基　　金：funded by the National Key R&D Program of China under grant No.2022YFA1603103;partially funded by the Regional Collaborative Innovation Project of Xinjiang Uyghur Autonomous Region under grant No.2022E01050;the Tianshan Talent Program of Xinjiang Uygur Autonomous Region under grant No.2022TSYCLJ0005;the Natural Science Foundation of Xinjiang Uygur Autonomous Region under grant No.2022D01E06;the Chinese Academy of Sciences(CAS)Light of West China Program under grants Nos.xbzg-zdsys-202212,2020-XBQNXZ-017,and 2021-XBQNXZ-028;the National Natural Science Foundation of China(NSFC,grant Nos.12173075,11973076,and 12103082);the Xinjiang Key Laboratory of Radio Astrophysics under grant No.2022D04033;the Youth Innovation Promotion Association CAS;funded by the Chinese Academy of Sciences Presidents International Fellowship Initiative under grants Nos.2022VMA0019 and 2023VMA0030;funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan under grant No.AP13067768。

摘　　要：The excitation temperature T_(ex)for molecular emission and absorption lines is an essential parameter for interpreting the molecular environment.This temperature can be obtained by observing multiple molecular transitions or hyperfine structures of a single transition,but it remains unknown for a single transition without hyperfine structure lines.Earlier H_(2)CO absorption experiments for a single transition without hyperfine structures adopted a constant value of T_(ex),which is not correct for molecular regions with active star formation and H II regions.For H_(2)CO,two equations with two unknowns may be used to determine the excitation temperature T_(ex)and the optical depthτ,if other parameters can be determined from measurements.Published observational data of the4.83 GHz(λ=6 cm)H_(2)CO(1_(10)-1_(11))absorption line for three star formation regions,W40,M17 and DR17,have been used to verify this method.The distributions of T_(ex)in these sources are in good agreement with the contours of the H110αemission of the H II regions in M17 and DR17 and with the H_(2)CO(1_(10)-1_(11))absorption in W40.The distributions of T_(ex)in the three sources indicate that there can be significant variation in the excitation temperature across star formation and H II regions and that the use of a fixed(low)value results in misinterpretation.

关 键 词：ISM molecules-(ISM )HII regions-ISM CLOUDS 

分 类 号：P14[天文地球—天体物理]