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 Title: DETECTION OF CH3CN IN DIFFUSE CLOUD TOWARD GALACTIC CENTER SGRB2(M) Author(s): Araki, Mitsunori Contributor(s): Tsukiyama, Koichi; Kamegai, Kazuhisa; Kuze, Nobuhiko; Oyama, Takahiro; Minami, Yoshiaki; Takano, Shuro Subject(s): Astronomy Abstract: Organic molecules have been detected mainly in dense clouds. As diffuse clouds are a previous phase of dense clouds in evolutionary history of interstellar clouds, detection of organic molecules in diffuse clouds can reveal a longer history of organic molecules. Despite of its importance, emission lines from molecules in diffuse clouds are difficult to detect because of inactive excitation by collisions and active cooling by radiations. However, for CH$_{3}$CN, a rotation around a molecular axis cannot be cooled by radiations. Thus, this molecule can be detected by absorption having a relatively strong line from $J = K$ rotational levels, because these levels are well populated. In our previous work, this rotational behavior was formulated as Hot Axis Effect" [1]. In this work, to detect this molecule in diffuse clouds that are more diffuse than the known diffuse clouds carrying organic molecules [2], we have been searched for absorption lines of the $J_{K}$ = 4$_{3}$–3$_{3}$ transition of CH$_{3}$CN at 73 GHz toward the galactic center SgrB2(M) by using Nobeyama 45 m telescope. As a result, this transition was detected in the diffuse cloud of SgrB2 envelop. The column density was derived to be 2 $\times$ 10$^{14}$ cm$^{-2}$. Therefore, we detected an organic molecule in the diffuse cloud that are more diffuse than the known diffuse cloud carrying CH$_{3}$CN [2] because this molecule detected shows the low excitation temperature of $\sim$ 3 K and the high kinetic temperature of $\sim$ 70 K. [1] Araki et al. Astronomical Journal, 148, 87 (2014) [2] Muller et al., A$\&$A, 535, 103 (2011) Issue Date: 06/21/18 Publisher: International Symposium on Molecular Spectroscopy Citation Info: APS Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/100614 DOI: 10.15278/isms.2018.RL05 Other Identifier(s): RL05 Date Available in IDEALS: 2018-08-172018-12-12
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