Multiple HC3N line observations towards 19 Galactic massive star-forming regions

We performed observations of the HC3N (24–23, 17–16, 11–10, 8–7) lines towards a sample consisting of 19 Galactic massive star-forming regions with the Arizona Radio Observatory 12 m and Caltech Submillimeter Observatory 10.4 m telescopes. HC3N (24–23, 17–16, 11–10, 8–7) lines were detected in sources except for W 44, where only HC3N (17–16, 11–10) were detected. Twelve of the nineteen sources showed probable line wing features. The excitation temperatures were estimated from the line ratio of HC3N (24–23) to HC3N (17–16) for 18 sources and are in the range 23– 57 K. The line widths of higher-J transitions are larger than lower-J ones for most sources. This indicates that the inner dense warm regions have more violent turbulence or other motions (such as rotation) than outer regions in these sources. A possible cutoff tendency was found around LIR ∼ 106 L⊙ in the relation between LIR and full width at half maximum line widths.