Carbon Chain Chemistry in Hot-core Regions around Three Massive Young Stellar Objects Associated with 6.7 GHz Methanol Masers

Abstract We have carried out observations of CCH ( N = 1 ? 0), CH 3 CN J 5 4), and three 13 C isotopologues HC 10 9) toward massive young stellar objects (MYSOs), G12.89+0.49, G16.86?2.16, G28.28?0.36, with the Nobeyama 45 m radio telescope. Combined previous results on N, column density ratios (CCH)/ (HC N), hereafter CCH/HC ratios, in MYSOs are derived to be ?15. This value is lower than that a low-mass warm carbon chain chemistry (WCCC) source by more one order magnitude. compare observed hot-core model calculations. The can best reproduced models when gas temperature ?85 K, which higher L1527, WCCC (?35 K). These suggest carbon-chain molecules detected around exist at least partially regions those sources. There no significant difference among G12.89+0.49 G16.86-2.16, while HCC abundant others G28.28–0.36. discuss based ratio isotopic fractionation N.