Survey Observations to Study Chemical Evolution from High-mass Starless
  Cores to High-mass Protostellar Objects I: HC3N and HC5N
  We carried out survey observations of HC$_{3}$N and HC$_{5}$N in the 42$-$45
GHz band toward 17 high-mass starless cores (HMSCs) and 35 high-mass
protostellar objects (HMPOs) with the Nobeyama 45 m radio telescope. We have
detected HC$_{3}$N from 15 HMSCs and 28 HMPOs, and HC$_{5}$N from 5 HMSCs and
14 HMPOs, respectively. The average values of the column density of HC$_{3}$N
are found to be ($5.7 \pm 0.7$)$\times 10^{12}$ and ($1.03 \pm 0.12$)$\times
10^{13}$ cm$^{-2}$ in HMSCs and HMPOs, respectively. The average values of the
fractional abundance of HC$_{3}$N are derived to be ($6.6 \pm 0.8$)$\times
10^{-11}$ and ($3.6 \pm 0.5$)$\times 10^{-11}$ in HMSCs and HMPOs,
respectively. We find that the fractional abundance of HC$_{3}$N decreases from
HMSCs to HMPOs using the Kolmogorov-Smirnov test. On the other hand, its
average value of the column density slightly increases from HMSCs to HMPOs.
This may imply that HC$_{3}$N is newly formed in dense gas in HMPO regions. We
also investigate the relationship between the column density of HC$_{3}$N in
HMPOs and the luminosity-to-mass ratio ($L/M$), a physical evolutional
indicator. The column density of HC$_{3}$N tends to decrease with increasing
the $L/M$ ratio, which suggests that HC$_{3}$N is destroyed by the stellar
activities.
