Multiple HC$_3$N line observations towards 19 Galactic massive
  star-forming regions
  We performed observations of the HC$_3$N (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. HC$_3$N (24-23, 17-16, 11-10, 8-7) lines were detected in sources
except for W44, where only HC$_3$N (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 HC$_3$N (24-23) to HC$_3$N
(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 $L_{\rm IR}$ $\sim$ 10$^{6}$
$L_\odot$ in the relation between $L_{\rm IR}$ and full width at half maximum
line widths.
